Which of these is NOT considered a variable cost?

Variable costs are expenses that change in direct proportion to the level of production or sales. They fluctuate based on operational output. In contrast, fixed costs remain constant regardless of the business's level of activity.

Salaries of permanent staff are generally considered fixed costs. They do not vary with production levels; these employees are paid a consistent wage regardless of how much product is made or sold. This makes the salaries of permanent staff distinctly different from costs that would change with production volume, such as raw materials and utility costs, which increase with higher usage or production.

In contrast, raw materials and utility costs based on usage are both examples of variable costs, as they increase or decrease depending on the level of production. Maintenance costs of machinery can also vary, but they don’t necessarily change in the same way as variable costs associated with each unit produced. It is the fixed nature of the salaries of permanent staff that categorizes them clearly as not being a variable cost.