We had a cnc turning center go down because a motor cooling fan went out. Would have been a several hundred dollar repair. I pulled the fan and got the bearings out. Allied wanted something like $18 per. A quick Google search and I realized they were the same bearings used in skateboard wheels. A jump across town and a $4 bill and we were back in business!
I used or rebuild bearings on cooling fans for power supplies used in a print shop somewhere. The bearings would get stiff and shut down the supply. For whatever reason, we couldn't find a fan with the correct encoder output to work with the supply. It was a $12 fan, if we could have found one. Instead, I had to disassemble, clean, and repack tiny bearings. Good times.