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.
I bought a $5 mechanical watch as aliexpress, curious how long it would last. That was 12y ago. All I replaced was the strap by a $1 one, still ok as well.
The $200 watch I bought before that was b0rken in 2 months.