Costs and cost behaviour

Welcome to the World of Costs!

Ever wondered how a business decides what price to charge for a product? Or how they know if they are actually making a profit? It all starts with understanding costs. In this chapter, we explore how costs behave and how we track the materials and labor that go into making things. Don't worry if this seems a bit mathematical at first—once you see the patterns, it becomes much easier!

1. Classifying Costs by Behaviour

Cost behaviour refers to how a cost changes when the level of activity (like the number of items produced) changes. Understanding this helps managers plan for the future.

Fixed Costs

These stay the same in total, regardless of how many items you make or sell. Example: The rent for your factory. Whether you make 1 shirt or 1,000 shirts, the landlord still wants the same amount of money.

Variable Costs

These change in direct proportion to the level of activity. If you produce more, the total cost goes up. Example: Raw materials. If one shirt requires \( \$5 \) worth of fabric, 10 shirts will cost \( \$50 \).

Stepped Costs

These stay fixed for a certain level of activity but then jump to a higher level once a limit is reached. Example: Hiring a supervisor. One supervisor can manage 10 workers. If you hire the 11th worker, you must hire a second supervisor, and your "fixed" supervision cost jumps up.

Semi-variable Costs

These contain both a fixed and a variable element. They are also known as "mixed costs." Example: A phone bill. You pay a basic monthly line rental (fixed) plus a charge for every minute you talk (variable).

Quick Review:
- Fixed: Stays the same in total.
- Variable: Increases as production increases.
- Stepped: Jumps at specific intervals.
- Semi-variable: Has a "base" cost plus an extra cost per unit.

2. Direct vs. Indirect Costs (Traceability)

Sometimes we categorize costs by how easily we can "trace" them to a specific product.

Direct Costs

These can be directly identified with a specific unit of production.
- Direct Materials: The wood used to make a table.
- Direct Labour: The wages of the carpenter who built that specific table.

Indirect Costs (Overheads)

These are costs that help the business run but cannot be easily linked to one specific item.
- Indirect Materials: The glue used in the factory (too small to track per table).
- Indirect Labour: The salary of the factory security guard.

The Prime Cost Formula:
\( \text{Direct Materials} + \text{Direct Labour} + \text{Direct Expenses} = \textbf{Prime Cost} \)

3. Inventory Valuation: FIFO and AVCO

Prices of raw materials often change. If you bought plastic at \( \$2 \) last week and \( \$3 \) this week, which price do you use when you sell the finished product? The syllabus requires you to know two methods:

FIFO (First-In, First-Out)

This method assumes that the oldest items in stock are used or sold first.
- Logic: Think of a milk fridge in a supermarket. The oldest milk is at the front so it sells first.
- Result: The closing inventory is valued at the most recent prices.

AVCO (Weighted Average Cost)

This method calculates a new average cost every time new stock is purchased (Perpetual) or at the end of a period (Periodic).
- Logic: Think of mixing different batches of paint in a bucket. Once mixed, you can't tell which was cheaper; they all have one average price.
- The Formula:
\( \text{Average Cost} = \frac{\text{Total Value of Stock on Hand}}{\text{Total Quantity of Stock on Hand}} \)

Perpetual vs. Periodic

- Perpetual: You update the value after every single transaction.
- Periodic: You wait until the end of the month to calculate the value of everything you have.

Common Mistake to Avoid: Don't forget to subtract the units sold from the quantity when calculating the new average in AVCO!

4. Accounting for Labour Costs

Labour isn't just about a monthly salary. Businesses use different ways to pay workers:

- Time Rate: Paying by the hour (e.g., \( \$10 \) per hour).
- Piece Rate: Paying for each item made (e.g., \( \$2 \) per shirt). This encourages speed but can sometimes lower quality.

Did you know? Idle time (when workers are at work but cannot produce due to a machine breakdown) is usually treated as an indirect cost (overhead) because no specific product was being made during that time.

5. Just-in-Time (JIT) Inventory Management

JIT is a modern approach where a business keeps minimal or zero inventory. Materials arrive exactly when they are needed for production.

Why use JIT?
- Reduces storage costs (no big warehouses needed).
- Reduces the risk of stock becoming obsolete or damaged.

The Risk:
- If a supplier is late or a delivery truck breaks down, the entire production line stops because there is no "buffer" stock.

Summary: Key Takeaways

1. Costs are either Fixed (total stays same), Variable (total changes), Stepped, or Semi-variable.
2. Direct costs (Prime Cost) are traceable; Indirect costs (Overheads) are not.
3. FIFO sells the old stuff first; AVCO averages the cost of everything.
4. JIT aims to eliminate waste by holding as little stock as possible.

Keep practicing the FIFO and AVCO tables—they are a favorite in exams! Once you get the rhythm of the calculations, you'll be flying.