What is something really stupid you purchased that turned out far better than expected?
I bought a piece of 1.5 inch stiff foam to try to fix a sag in a bed. It didn't work but having that thick piece of solid foam around has been a life saver.
Need something flat to put a laptop on? Throw it on the foam. Going to be doing something that requires you to be on your knees for a while? Get the foam!
It went from stupid purchase to something I'd gladly replace if it broke.
An old Asus Chromebox CN60, I bought it because it was dirt cheap, as should probably be expected EOL ChromeOS device.
It seems like something that would be completely and utterly useless but once I put Linux on it I was able to use it as a handy little Server. I guess I didn't really think that it was stupid, but other people thought that it was stupid that I bought it.
I had an Acer netbook that I ended up calling the Netbook of Theseus because I bought one in 2009, then several years later bought an identical one on eBay. I ran Linux on the thing and kept it until last year.
Oh, I bought the second one for parts but it turned out to be in better shape than my old one. So I moved a bunch of the parts from the first one over to the second, because neither was working before I did that.