A fixed cost spread over fewer units raises the average unit cost. That matters for capacity budgeting, although it does not mean one extra unit costs that average to make.
An example with numbers
If each unit uses $6 of materials and the workshop costs $3,000 a month, producing 1,000 units gives an average cost of $9. Producing 500 raises the average cost to $12, with the same fixed costs.
Try it with your numbers
Set up three volume scenarios. Keep the variable cost per unit, the month's fixed cost and the resulting average cost separate.
Example figures for learning purposes. They are not a recommendation and do not replace professional advice.