Oh, I always win at Book Off in Japan. If you don't know what that is, give it a search. It's an interesting place.

I've bought several expensive camera lenses for 8-20$. Since they have no electronic components, they work fine. I use them to document work I do for various people or myself as a marketing too for my business. Worth every last one of those 8 dollars! Some are worth quite a bit of money.

There's a vacuum tube on my desk worth a bit. I found it for 3$ in a junk bin. Turned out it worked, so I built a weird, cursed amplifier out of it as a joke, using some old Soviet scrap and mystery Chinese ICs. Probably not worth anything anymore! -- but hey, it's a tube amp that works entirely at 5V! So weird!

I have a beautiful set of unused old ink stones from a famous manufacturer in China. I paid around 10$ for it. These are actually quite expensive and worth hundreds of dollars. Certainly less than a thousand though.

I also have a singing bowl, made of cast bronze. I don't know much about it, except it's old enough to predate modern machining (it was clearly sand-cast). It's probably also cursed -- someone sold it to me by accident for a few dollars when I asked for something else. Then I didn't notice until I got home. It's probably worth some money to the right person, but few people value such old things in my country and I don't want to sell it to an overseas buyer.

Oh and I have one of the original victory fliers from when the Japanese defeated the Russians in 1904. In perfect condition. I have no idea what it's worth, but certainly much more than I paid for it, haha. I should probably find a museum for it one day.