Short runs cost more per unit because setup and makeready are fixed. The same prep and machine setup whether you run 50 or 500 means the cost per piece is higher at 50.
Fixed vs variable cost
Setup, plates, and makeready are fixed per job. Paper and ink scale with quantity. So the total cost rises less than proportionally with quantity; the per-unit cost falls as quantity goes up.
When short runs make sense
When you need a small quantity for a test, an event, or a one-off, paying more per unit can still be the right choice. When you will reorder or need volume, ordering more (or planning reorders) reduces per-unit cost.
To reduce per-unit cost
• Increase quantity if you will use the pieces.
• Use standard sizes and options to avoid custom setup where possible.
• Combine multiple items into one run if the printer can gang them.
Common mistake
Comparing per-unit price of a short run to a long run and expecting them to match. They cannot; the economics are different. Compare same quantity to same quantity.