5.4 Costs

Costs are sacrifices incurred to produce or sell output. Fixed costs do not change directly with output in the short run; variable costs change with activity; total cost combines both.

Classifying costs helps price, budget, outsource, compare options and assess break-even. A cost can behave differently at different scales or time horizons.

Rent may be fixed within current capacity, while packaging rises with units. If a second site is opened, rent may become a step cost.

Fixed does not mean permanent, and variable does not mean every unit costs exactly the same.

Job, batch, unit and process costing assign or average costs in different production contexts. The approach should match the traceability, variety and volume of the output.

A costing method influences pricing and profitability information; it is a model of resource use, not a perfect measure of economic value.

A bespoke consultancy can trace labour and materials to one job, while a continuous chemical process may average costs across a large output stream.

A cost per unit is only meaningful when the cost pool and output basis are clearly defined.

Managers use cost information to set prices, prepare budgets, compare alternatives, control waste and evaluate performance. The useful measure depends on the decision and time horizon.

Relevant costs are future costs that change between options; sunk costs should not drive a new decision, while opportunity costs capture what is forgone.

When deciding whether to accept a one-off order, spare capacity and incremental cost matter more than a historical development cost that will not change.

A full allocated cost can be useful for reporting but misleading for a short-term decision if it does not change.

Break-even is the output where total revenue equals total cost. It depends on fixed costs, selling price and variable cost per unit; contribution per unit is price minus variable cost.

Break-even analysis shows the output needed to avoid an accounting loss and how safety margin changes when assumptions change.

If price is £10, variable cost £6 and fixed cost £2,000, contribution is £4 and break-even is 500 units. A price cut changes the calculation even if demand rises.

Break-even is a model based on assumptions such as constant price and unit cost; real demand and capacity may not behave linearly.