Relevant Costing and Short-Term Decisions

Introduction and Context

Managers frequently face decisions that do not require a complete redesign of the business but may materially affect short-term profitability: whether to manufacture a component or purchase it, accept a one-time order, discontinue a product, replace equipment, allocate scarce capacity, or alter a price. Financial accounting reports are essential for stewardship and external reporting, but they often contain allocated fixed costs, sunk costs and historical amounts that are not relevant to the immediate decision.

Relevant costing provides a disciplined way to isolate the future cash flows that differ between alternatives. It is therefore a decision-support technique rather than a replacement for full financial accounting. Its central managerial question is: Which future revenues and costs will change as a consequence of choosing one alternative rather than another?

The analysis is especially valuable in operations management because operational choices involve capacity, bottlenecks, supplier relationships, quality, lead time, resilience, compliance and strategic capability. A numerically attractive decision may be operationally harmful if it ignores these factors.

Learning Objectives

By the end of this chapter, the reader should be able to:

1. Define relevant, irrelevant, sunk, avoidable, unavoidable and opportunity costs.
2. Apply contribution analysis to make-or-buy, outsourcing, special-order, shutdown, product-mix, pricing and replacement decisions.
3. Incorporate opportunity costs and capacity constraints into short-term decisions.
4. Distinguish short-run decision analysis from long-run strategic costing.
5. Use sensitivity analysis and qualitative judgement to test recommendations.
6. Evaluate ethical, operational and governance risks in relevant-cost decisions.

1. The Logic of Relevant Costing

A cost is relevant to a decision when it satisfies both conditions below:

• it relates to the future; and
• it differs between the alternatives under consideration.

A relevant benefit follows the same logic: it is a future benefit that differs between alternatives. The relevant net advantage of an alternative can be expressed as:

The comparison should be made between alternatives, not against an abstract total-cost figure. If Alternative A produces an incremental contribution of $80,000 and Alternative B produces $60,000, A is preferable by $20,000, provided the alternatives have comparable risk and no binding non-financial constraint is violated.

1.1 Important cost classifications

Allocated fixed overhead is not automatically relevant or irrelevant. Its treatment depends on whether the allocation represents an actual change in total cost. For example, a $12,000 share of corporate rent may be irrelevant if the rent continues under either alternative. Conversely, a supervisor’s salary may be relevant if the supervisor position can be eliminated.

1.2 Relevant cost versus full cost

Full cost commonly includes direct materials, direct labour, variable overhead and an allocation of fixed overhead. It is useful for inventory valuation, performance reporting and long-run pricing. Relevant cost excludes amounts that do not change and adds opportunity costs that may not appear in accounting records.

A decision should not be based mechanically on unit cost. Unit costs can change when volume changes because fixed costs are spread over a different number of units. The decision should instead compare total future consequences over the relevant decision horizon.

1.3 Contribution margin

Contribution margin is the amount available to cover fixed costs and profit:

Per-unit contribution margin is:

These formulas assume that selling price and variable cost per unit are stable over the relevant range. Contribution analysis is particularly useful when fixed costs are unchanged and capacity is available. When capacity is scarce, contribution per unit of the constrained resource is more informative:

2. A General Decision Framework

A robust relevant-cost analysis follows these steps:

1. Define the decision, alternatives and time horizon.
2. Identify technical and operational constraints, including capacity and service requirements.
3. List future revenues and costs under each alternative.
4. Remove sunk and common costs.
5. Add avoidable costs and opportunity costs.
6. Quantify the differential financial effect.
7. Test sensitivity to uncertain assumptions.
8. Evaluate qualitative, strategic, ethical and risk implications.
9. Implement, monitor and compare actual outcomes with the decision model.

The time horizon matters. A fixed cost may be unavoidable over three months but avoidable over three years. Relevant costing is therefore conditional on the decision horizon and the organization’s ability to change resources.

3. Make-or-Buy and Outsourcing Decisions

A make-or-buy decision compares internal production with external purchasing. The correct comparison is not usually the supplier’s quoted price against the internal full absorption cost. It is the purchase price against the internal costs avoided by buying, plus any opportunity cost of using internal capacity.

The basic condition for buying is:

If internal capacity is idle and has no alternative use, opportunity cost is zero. If the capacity could produce another item, the forgone contribution from that item is an opportunity cost.

Worked example: component sourcing

A manufacturer requires 10,000 components. Internal unit costs are:

A supplier offers the component for $41. Of the fixed overhead, only $4 per unit is avoidable. The remaining $6 continues regardless of the decision. Internal capacity has no alternative use.

Avoidable internal cost per unit is:

$18 + $12 + $6 + $4 = $40

Buying costs $41 per unit, so making saves $1 per unit. For 10,000 units, making has a financial advantage of $10,000. The allocated full cost of $46 would incorrectly suggest that buying is cheaper by $5 per unit.

If the released capacity could instead produce a product generating $3 contribution per component-equivalent unit, the opportunity cost of making would be $3. The relevant cost of making would become $43 per unit, and buying would be preferable by $2 per unit.

Outsourcing analysis must also consider quality, intellectual property, supplier dependence, capacity recovery, labour obligations, transport emissions, cybersecurity, delivery reliability and switching costs. A supplier price that is lower today may not be lower after expediting, inspection, warranty claims or contract administration.

4. Special Orders and Incremental Business

A special order is usually a non-recurring order offered at a price different from the normal market price. It should be accepted when its incremental revenue exceeds incremental relevant cost, subject to capacity and strategic constraints.

If idle capacity exists and the order does not affect normal sales:

The order should not normally be charged with allocated fixed costs that will remain unchanged. However, a special order may require additional tooling, inspection, setup, certification, logistics or customer service; these costs are relevant.

Worked example: special order with a capacity constraint

A plant has 2,000 unused machine hours. A customer offers an order requiring 1,500 hours and 3,000 units at $28 each. Variable cost is $21 per unit, and the order requires a one-time setup cost of $5,000.

Incremental revenue is $3,000 × $28 = $84,000. Incremental variable cost is $3,000 × $21 = $63,000. Incremental contribution before setup is $21,000; after setup it is $16,000. The order is financially attractive if it does not reduce regular sales and does not create unacceptable operational risks.

If the plant were fully utilized, accepting the order would require sacrificing another product’s contribution. That lost contribution becomes an opportunity cost and may reverse the decision.

Managers should be cautious when a discounted special-order price may leak into the regular market, establish a damaging reference price, or consume scarce technical capacity needed for strategic customers.

5. Shutdown, Continue or Discontinue Decisions

A temporary shutdown decision compares the contribution lost by stopping operations with the fixed costs avoided by shutting down. The relevant condition for continuing is:

Equivalently, shut down if the contribution margin is less than the avoidable fixed costs, assuming shutdown does not create additional costs or destroy future capability.

A product-line discontinuation requires the same logic. A product may report a loss after allocated corporate costs but still contribute positively toward those costs. Discontinuation improves profit only when the avoidable costs exceed the contribution margin lost.

Example: product-line decision

Product X generates sales of $500,000 and variable costs of $320,000. Its contribution margin is $180,000. Allocated fixed costs are $210,000, producing a reported loss of $30,000. Investigation shows that only $120,000 of fixed costs would be avoided if X were discontinued.

Continuing X improves total profit by:

$180,000 − $120,000 = $60,000

Discontinuing it would reduce profit by $60,000, unless the resources could be redeployed to an alternative generating more than $60,000 contribution.

Shutdown decisions also require consideration of restart costs, workforce capability, customer relationships, regulatory permits, maintenance and asset deterioration. A temporary shutdown may be financially attractive but strategically expensive.

6. Product Mix Under a Bottleneck

When demand exceeds capacity, products should be ranked by contribution per unit of the scarce resource rather than contribution per unit of product. The constrained resource may be machine hours, skilled labour hours, warehouse space, testing capacity or a critical material.

Worked example: machine-hour constraint

If demand exists for all products and machine hours are scarce, the priority is B, C, then A. This ranking maximizes contribution only under assumptions that demand is available, products are divisible or produced in feasible batches, other constraints are absent, and fixed costs do not change.

A more advanced formulation is a linear programming model. Let x_i be units of product i, c_i its unit contribution, and a_i the scarce resource required per unit. With capacity H:

Additional constraints may include demand limits, minimum contractual volumes, labour availability and material balances. Shadow prices from such a model estimate the value of one additional unit of bottleneck capacity, within the valid range of the model.

7. Short-Term Pricing Decisions

Short-term pricing differs from long-run pricing. In the short run, a price may be acceptable if it covers incremental relevant costs and makes a positive contribution, provided unused capacity exists and normal demand is protected. In the long run, prices must recover capacity, development, support, financing and strategic costs.

For a target contribution margin ratio m and price P, the maximum variable cost compatible with the target is:

This is a planning relationship, not a universal pricing rule. Market willingness to pay, competitive response, customer segmentation, capacity, product positioning and legal restrictions also matter.

Predatory pricing, discriminatory pricing without legitimate grounds, misleading quotations and prices that conceal unsafe or non-compliant practices create ethical and legal risks. A pricing decision should document assumptions and approval authority, particularly when a price is below reported full cost.

8. Replacement and Equipment Decisions

Replacement analysis compares keeping existing equipment with acquiring new equipment. The original purchase cost and accumulated depreciation of the existing asset are sunk for the replacement decision. The current disposal value of the existing asset is relevant because keeping it sacrifices the cash that could be obtained by selling it.

A simplified comparison over a common planning horizon is:

If cash flows occur at different times, present value should be used. For a cash flow CF_t received or paid at time t and discount rate r,

The sign convention must be consistent: benefits may be treated as positive and costs as negative, or all amounts may be expressed as costs. The discount rate and horizon should reflect the organization’s approved capital evaluation policy. Replacement is a longer-term decision than a typical special order, so tax, financing, maintenance reliability, energy use, residual value and technological obsolescence may be material.

9. Sensitivity and Scenario Analysis

Relevant-cost decisions are often based on uncertain prices, demand, labour rates, reliability and capacity. Sensitivity analysis changes one assumption at a time to identify the break-even value. Scenario analysis changes several linked assumptions to represent plausible futures.

For a decision with incremental fixed cost F, unit price P and unit variable cost V, the break-even volume is:

This formula assumes constant unit price and variable cost, no capacity limit, and a single relevant product. If the contribution margin is zero or negative, no finite positive break-even volume exists under these assumptions.

For the make-or-buy example, the supplier price at indifference is $40 per component when capacity has no alternative use. If internal capacity could generate $3 contribution elsewhere, the indifference purchase price becomes $43. Such thresholds help managers negotiate and identify which assumptions deserve verification.

A useful decision memorandum should show:

• base-case recommendation;
• key assumptions;
• break-even or indifference thresholds;
• downside and upside scenarios;
• probability information where credible;
• non-financial risks; and
• a monitoring trigger for revisiting the decision.

10. Integrated Illustrative Case: Orion Appliances

This is a fictional illustrative case.

Background

Orion Appliances produces commercial refrigeration units. A control module is currently manufactured internally at a reported cost of $92 per unit. An external supplier offers the module for $84. Annual demand is 20,000 units. Internal production uses 0.4 hours of electronic assembly capacity per module. The plant has 9,000 available hours, while current products require 8,000 hours.

The internal cost per module is:

Of the fixed overhead, $8 per unit is avoidable if production stops. The remaining fixed cost is committed for the year. A redesigned premium module could be produced using released capacity and would generate $30 contribution per assembly hour. The supplier has a 97% on-time delivery rate, compared with Orion’s 99.5% internal rate.

Problem

Should Orion buy the standard module, continue making it, or outsource only part of the requirement while using capacity for the premium module?

Analysis

For the first 2,500 modules, Orion has spare capacity: 1,000 unused hours divided by 0.4 hours per module. The relevant internal cost is:

$38 + $22 + $10 + $8 = $78

Buying at $84 is $6 more expensive than making for these units.

For the remaining 17,500 modules, internal production would consume hours that could be used for the premium module. The opportunity cost per standard module is:

$0.4 × $30 = $12

The relevant cost of making these units is therefore $90 per unit: $78 avoidable production cost plus $12 opportunity cost. Buying at $84 is financially preferable by $6 per unit for this portion.

The annual financial comparison is:

The mixed strategy also releases 7,000 hours for the premium module: 17,500 × 0.4. If premium demand exists and the $30 contribution is realistic, the opportunity cost is economically valid.

Approach and solution

Orion should make 2,500 standard modules using spare capacity and buy 17,500, subject to supplier qualification. Before implementation, it should negotiate service-level agreements, quality guarantees, emergency supply provisions and audit rights. Because the supplier’s delivery reliability is lower, Orion should assess safety stock and the cost of disruption. If holding inventory or expediting costs exceed the $105,000 outsourcing advantage, the recommendation must be revised.

Outcome and learning points

The case demonstrates that one decision can have different relevant costs at different capacity levels. It also shows why the supplier’s price cannot be compared only with reported full cost. A sound recommendation combines avoidable cost, opportunity cost, capacity economics and operational risk.

11. Limitations, Governance and Contemporary Practice

Relevant costing is a model, not an exact representation of reality. Its main limitations include:

• uncertain demand and cost estimates;
• nonlinear costs at capacity limits;
• quality and reliability effects that are difficult to monetize;
• strategic capabilities lost through outsourcing;
• behavioural responses by employees, suppliers and customers;
• interdependencies among products and processes; and
• risk that managers manipulate assumptions to justify a preferred outcome.

Governance requires transparent assumptions, separation of facts from estimates, documented approval, review of conflicts of interest and post-decision evaluation. Managers should not deliberately exclude foreseeable safety, environmental, labour or compliance costs merely because they are difficult to quantify.

Digital costing systems and AI-enabled analytics can improve scenario speed by integrating production data, supplier performance, machine availability and demand forecasts. However, automated recommendations remain dependent on data quality, model boundaries and human oversight. AI should not be treated as evidence that a cost is relevant; relevance remains a conceptual judgement about future differential consequences.

Best practice is to combine a concise quantitative model with an operational risk register, sensitivity analysis and explicit decision rights. The model should be updated when prices, capacity, regulations or strategic priorities change.

Chapter Summary

Relevant costing identifies future revenues and costs that differ among alternatives. Sunk and unavoidable costs are excluded, while avoidable and opportunity costs are included. Contribution margin is central to special-order, shutdown and product-mix analysis, but scarce resources require ranking contribution per bottleneck unit. Make-or-buy decisions compare supplier price with avoidable internal cost and the opportunity cost of capacity, not automatically with full absorption cost. Replacement decisions exclude the original asset cost but include current disposal value and future operating differences. Pricing must distinguish short-run incremental decisions from long-run cost recovery and market strategy. Sensitivity analysis identifies break-even assumptions and exposes risk. Finally, financial results must be integrated with quality, resilience, ethics, compliance, workforce and strategic-capability considerations.

Key Terms

Relevant cost: A future cost that differs between decision alternatives.

Relevant revenue: Future revenue that differs between alternatives.

Sunk cost: A past cost that cannot be recovered.

Differential cost: The difference in cost between alternatives.

Incremental cost: Additional cost caused by an increase in activity or a decision.

Avoidable cost: A cost eliminated by selecting a particular alternative.

Unavoidable cost: A cost that remains regardless of the decision.

Opportunity cost: The benefit sacrificed by using a resource for one purpose rather than its best alternative use.

Committed cost: A cost arising from a prior commitment and not readily changeable in the short run.

Contribution margin: Sales revenue less variable costs.

Bottleneck: A constrained resource limiting system output.

Product mix: The combination and quantity of products produced or sold.

Special order: A non-routine order evaluated using incremental consequences.

Make-or-buy decision: A choice between internal production and external purchase.

Outsourcing: Obtaining an activity, product or service from an external provider.

Shutdown decision: A choice to suspend operations temporarily or permanently.

Full cost: Total cost including assigned direct and indirect costs.

Sensitivity analysis: Testing the effect of changing one or more assumptions.

Shadow price: The estimated value of one additional unit of a constrained resource.

Relevant horizon: The time period over which costs and benefits can change for the decision.

Review Questions

Short Answer Questions

1. What two conditions must a cost satisfy to be relevant?
2. Why is allocated fixed overhead not automatically relevant?
3. Define opportunity cost and explain its role in product-mix decisions.
4. Why may a product showing an accounting loss still be worth retaining?
5. Distinguish short-run incremental pricing from long-run pricing.

Long Answer Questions

1. Explain a systematic framework for analysing make-or-buy decisions, including quantitative and qualitative factors.
2. Discuss how bottlenecks affect product prioritization and explain the limitations of ranking products by contribution per constrained-resource unit.
3. Compare relevant costing with full absorption costing in managerial decision-making.
4. Explain the treatment of sunk costs, disposal proceeds and future operating costs in equipment replacement decisions.
5. Evaluate the governance and ethical risks of using relevant costing in outsourcing and shutdown decisions.

Analytical / Application Questions

1. A component can be made for $26 of materials, $15 of labour, $7 of variable overhead and $9 of allocated fixed overhead. Only $3 of fixed overhead is avoidable. A supplier quotes $50. Internal capacity can produce another item generating $8 contribution for each component-equivalent unit. Should the component be made or bought? Show the relevant-cost calculation.
2. Product P contributes $36 per unit and requires 2 machine hours. Product Q contributes $30 per unit and requires 1 machine hour. If 4,000 machine hours are available and demand is 1,000 units of P and 3,000 units of Q, determine the profit-maximizing mix, assuming no other constraints.
3. A special order offers 5,000 units at $19 each. Variable cost is $14 per unit, and accepting the order would require $12,000 of additional inspection cost. It would displace a regular order generating $9 contribution per unit for 1,000 units. Should the special order be accepted? Justify your answer using relevant costs.

Multiple Choice Questions with Answers

Question 1

Which cost is normally excluded from a short-term relevant-cost analysis?

A. Future avoidable labour cost

B. Opportunity cost of scarce capacity

C. Historical cost already incurred and unrecoverable

D. Additional transport cost caused by an alternative

Correct Answer: C. Historical cost already incurred and unrecoverable

Question 2

A product sells for $50 and has variable cost of $32. What is its unit contribution margin?

A. $18

B. $32

C. $50

D. $82

Correct Answer: A. $18

Question 3

A supplier quotes $41 per unit. Avoidable internal cost is $38 and unused capacity has no alternative use. What is the preferred financial choice, all else equal?

A. Buy, because full cost is always relevant

B. Make, because internal relevant cost is lower

C. Buy, because the quoted price exceeds variable cost

D. Neither, because fixed costs must be allocated

Correct Answer: B. Make, because internal relevant cost is lower

Question 4

When a machine-hour bottleneck exists, products should generally be ranked by:

A. Selling price per unit

B. Full cost per unit

C. Contribution per unit of bottleneck resource

D. Allocated overhead per unit

Correct Answer: C. Contribution per unit of bottleneck resource

Question 5

A product has contribution margin of $120,000 and avoidable fixed costs of $90,000. If no alternative use exists, discontinuing it will:

A. Increase profit by $30,000

B. Reduce profit by $30,000

C. Have no effect on profit

D. Increase profit by $90,000

Correct Answer: B. Reduce profit by $30,000

Question 6

Which item is relevant when deciding whether to replace an existing machine?

A. Original purchase price of the existing machine

B. Accumulated depreciation already recorded

C. Current disposal proceeds forgone by retaining the machine

D. Historical installation cost that cannot be recovered

Correct Answer: C. Current disposal proceeds forgone by retaining the machine

Question 7

A special order uses idle capacity and has price $24, variable cost $18, and additional setup cost $4,000 for 1,000 units. What is its incremental profit?

A. $2,000

B. $6,000

C. $10,000

D. $14,000

Correct Answer: A. $2,000

Question 8

If a resource can generate $12 contribution in its best alternative use, using it for another product creates:

A. A sunk cost of $12

B. An opportunity cost of $12

C. An unavoidable cost of $12

D. An allocated overhead cost of $12

Correct Answer: B. An opportunity cost of $12

Question 9

The break-even volume with fixed relevant cost F, price P and variable cost V is:

A. F × (P − V)

B. (P − V) ÷ F

C. F ÷ (P − V)

D. P ÷ (F − V)

Correct Answer: C. F ÷ (P − V)

Question 10

Why should a quantitative outsourcing recommendation be supplemented by qualitative analysis?

A. Relevant costing never uses numerical information

B. Quality, resilience and compliance effects may materially affect the decision

C. Allocated fixed costs must always be included

D. Opportunity costs cannot be calculated

Correct Answer: B. Quality, resilience and compliance effects may materially affect the decision