An extra capacitor for your air conditioner (if you have one). They’re like $20-$30.
Our AC stopped working today and we were very lucky there was a store relatively near us that had them in stock and would sell to homeowners (I guess some places only sell AC parts to contractors). Anyways, it was easy to replace, our AC is back, and we got an extra one for the next time we have to replace it.
Oof that is a big increase in price. But you saved a lot more doing it yourself than you would have calling someone to fix it.