Buy in bulk if it's cheaper per unit that you buy, and per unit if it's cheaper per unit that you use. (EDIT: with the understanding that you're unlikely to buy

Buy in bulk if it's cheaper per unit that you buy, and per unit if it's cheaper per unit that you use. (EDIT: with the understanding that you're unlikely to buy much more than you use if just-in-time per-unit purchasing is available). No, it's not groundbreaking advice, but it's a very easy trap to fall into, especially if you're talking to someone who's good at selling you stuff. I'm sure we've all had an experience at least once where we've bought something in a larger container from the grocery store thinking we were getting a deal, only to find that we didn't get through it as fast as we thought we would, it started spoiling, and we got to scrape our savings into the trash can. And many of us have had an experience where someone higher up in the company has insisted that we use a tool that isn't very good "because we've already paid for it", so it's clearly needed advice, even if it's not groundbreaking. Everyone sometimes needs "obvious" conclusions pointed out to them, I think. It's a quirk of our mental processing as humans.