A five-part requirement becomes a 25-part purchase.

How does five parts become 25? OK, here's the story. A project needs five identical circuit boards, but we're giving them one spare, so that's six. The effort in designing the PCB was rather substantial, and the PCB house cost for ordering 10 was the same as six, so we have 10 blank PCBs. This is good because we might be able to use this board in another project someday. There are a number of new surface-mount parts on the board, not in ordinary inventory, and it's time-consuming to order the parts, which means you only want to do it once, so certainly we're going to order at least 10 parts to populate all the PCBs, and maybe a spare part or two, plus while we're at it, checking orders, labeling inventory bottles, and etc., we'd like to have a few of these SMT parts for other projects, so the order quantity becomes 15. But upon placing the order it's discovered the price break is at 25 parts, and the price of each of the 10 parts from 15 to 25 is only 1/3 the price of the first 15 parts, well under 50 cents each, and given the time spent so far in the process, it makes good sense to get 25 parts. That's how five parts becomes 25.