A note on the management accounting theme of "different costs for different purposes"

A note on the management accounting theme of "different costs for different purposes"

 

Regarding the subject of advanced management accounting, an important theme is "different costs for different purposes". Please briefly clarify this theme with 2 illustrative examples.

“Different costs for different purposes” means that no single cost figure is suitable for every management-accounting task. The costs included should depend on the decision or objective—for example, setting a long-run price, accepting a one-off order, valuing inventory, controlling a department, or evaluating a manager’s performance.

A cost may therefore be highly useful in one setting but irrelevant in another. In particular, short-term decisions normally focus on future costs and benefits that change between alternatives (incremental, avoidable, and opportunity costs), rather than sunk costs or unavoidable fixed overheads.

Why the distinction matters

Management may need:

• Full product cost: direct materials, direct labour, variable overheads, and an appropriate share of fixed production overheads. This is useful for long-run pricing, profitability analysis, and inventory valuation.
• Relevant cost: only future cash flows that will differ because of the decision. This is useful for short-run decisions such as special orders, make-or-buy, or discontinuing a product.
• Controllable cost: costs a particular manager can influence. This is useful for responsibility accounting and performance evaluation.
• Budget/ standard cost: planned benchmarks used to control operations and investigate variances.

Example 1: Pricing a regular product

An online retailer sells a product with the following cost per unit:

Cost item	Cost per unit (HK$)
Purchase cost	80
Packaging and delivery handling	10
Variable selling cost	5
Allocated warehouse and platform overhead	15
Full cost	110

If the retailer is setting a normal, sustainable selling price, it should consider the full cost of HK$110. A price below HK$110 may cover immediate purchase and handling costs but may fail to recover warehouse rent, platform subscriptions, administration, and other fixed operating costs over time.

For example, applying a 30% mark-up on full cost gives:

Price=110×1.30=HK$143

Here, allocated fixed overhead is relevant because the purpose is long-run pricing and profitability—not simply whether to make one extra sale. Cost-plus pricing commonly requires both fixed and variable costs to be charged to the product.

Example 2: Accepting a one-off special order

Suppose the same retailer has unused capacity and receives a one-time order for 100 units at HK$105 each. The normal full cost remains HK$110 per unit.

For this short-run decision, the warehouse/ platform overhead of HK$15 per unit will be paid anyway, whether the special order is accepted or rejected. It is therefore not relevant to this particular choice.

Relevant item per unit	HK$
Special-order revenue	105
Purchase cost	(80)
Packaging and handling	(10)
Variable selling cost	(5)
Incremental contribution	10

The order generates:

100×10=HK$1,000

So the retailer should normally accept the order, assuming it has spare capacity, the order does not displace normal sales, and there are no hidden costs such as additional customer-service work or brand damage.

Although the special-order price of HK$105 is below the full cost of HK$110, it exceeds the relevant incremental cost of HK$95. The allocated warehouse/ platform overhead is not caused by accepting the order, while the extra purchase, packing, and selling costs are caused by it. Relevant costing therefore concentrates on costs and revenues that change as a consequence of the decision.

Key takeaway

The central question is not “What is the product’s cost?” but:

“Which costs are relevant for this particular purpose and decision?”

Using full cost for a one-off capacity decision could cause management to reject profitable business. Conversely, using only variable cost for long-run pricing could lead to prices that do not recover the organisation’s total operating cost.