Explain fixed, variable and total costs, calculate average (unit) cost, and explain economies and diseconomies of scale

What this dot point is asking

This outcome wants you to explain fixed, variable and total costs, to calculate the average (unit) cost, and to explain economies and diseconomies of scale. The central idea is that as a business grows and produces more, its average cost per unit usually falls (economies of scale), but if it grows too large, average cost can start to rise again (diseconomies of scale).

The answer

Types of cost

• Fixed costs do not change with output in the short term. Examples: rent, salaries, insurance. They must be paid even if nothing is produced.
• Variable costs change directly with output. Examples: raw materials, packaging, hourly wages. More output means higher variable costs.
• Total cost is fixed costs plus total variable costs:

Average (unit) cost

The average cost, or cost per unit, is:

As output rises, the fixed cost is spread over more units, so the fixed cost per unit falls, which usually pulls the average cost down - the basis of economies of scale.

Economies of scale

Economies of scale are the fall in average cost as a business grows and produces more. The main internal types are:

• Purchasing (bulk-buying) - lower prices for buying in large quantities.
• Technical - large, efficient machinery and continuous production.
• Financial - cheaper borrowing because large firms are seen as lower risk.
• Managerial - affording specialist managers who run things more efficiently.
• Marketing - advertising costs spread over far more units.

Diseconomies of scale

If a firm grows too large, average cost can rise. Diseconomies of scale include:

• Poor communication - messages get slow and distorted in a big organisation.
• Poor coordination - hard to control many sites and departments.
• Low morale - workers feel like a small part of a huge firm, reducing effort.

So average cost typically falls as a firm grows, reaches a low point, then rises if it expands beyond an efficient size.

Examples in context

Example 1. A large manufacturer's bulk buying. A big Singapore food manufacturer buys flour and sugar by the tonne, negotiating far lower prices per kilogram than a small bakery paying retail. This purchasing economy lowers its average cost, letting it sell branded products cheaply nationwide. The example shows how scale alone can cut unit costs and explains why large firms often out-compete small ones on price.

Example 2. Diseconomies in a fast-growing chain. A restaurant chain expands from 5 to 80 outlets very quickly. Head office struggles to keep quality and service consistent, communication slows, and some managers feel unsupported, so costs rise and standards slip in places. These diseconomies of scale show that growth can eventually raise average cost, which is why firms must manage expansion carefully rather than assume bigger is always better.

Try this

Q1. Define the term fixed costs. [2 marks]

• Cue. Fixed costs are costs that do not change with the level of output in the short term, such as rent, insurance and salaries, and must be paid even if the business produces nothing.

Q2. A firm has fixed costs of $3,000 and variable costs of$4 per unit. Calculate its total cost at 1,000 units. [2 marks]

• Cue. Total variable cost = 4 \times 1{,}000 = \4{,}000$; total cost =$\3{,}000 + \4{,}000 = \$7{,}000$.

Q3. Explain one economy of scale a large firm may gain as it grows. [4 marks]

• Cue. Purchasing (bulk-buying) economies: a large firm buys materials in big quantities and negotiates a lower price per unit from suppliers, because the supplier values the large, regular order. This lowers the firm's variable cost per unit, reducing its average cost, which allows it to charge lower prices or earn more profit than a small firm that buys in small amounts at higher prices.