Eventually, you’re going to need a button. Or a bolt. It’s a pain to have to make a special trip to a store to buy the one button you need to fix the shirt you need today. Likewise, when you find you need a bolt or a screw for some minor repair. It’s especially frustrating to have return to the same hardware store that you had been to just 2 hours earlier because you need one more bolt to finish your project.
If you have a jar full of buttons, there’s a good chance you can find one that’s close enough to do the job. A jar full of bolts and nuts, screws, and similar hardware is also very useful.
This is more a matter of saving time than money, but your time is worth a lot of money (isn’t it?). When you’re throwing away old clothes or old furniture or anything that has buttons, bolts, screws or any other kind of fasteners (and when you see these things that other people have thrown away), take a look and see if you can salvage some of those useful fasteners and add them to your home store.
Whenever I throw away an old shirt, I remove all the buttons and put them in the button jar. If I have several matching buttons I sometimes keep them together on bit of string or thread.
I can’t count the number of times I’ve added to my nut and bolt collection by just taking a few that are easy to remove from furniture that my neighbors have thrown away. I’ve also taken knobs from drawers and cabinets that I’ve found on the curb. And some hinges. And many of those cool IKEA fasteners and the little dowel rods. (It’s good to have carry a Swiss Army knife or multi-tool for this sort of thing.)
Keep stocking your home store with buttons and bolts that would otherwise end up in a landfill and it will serve you well.