Here is a lens that I purchased for $12, from a dealer who has sold me a lot of camera stuff over the years.
It is so well made, with slick operation - and so silky smooth, and its a Canon. You could put it in the display cabinet without even taking a picture.
I was taken by the F2 over 17 - 102mm. A lens like that today would cost a fortune. So I was prepared to lose $12 - but shipping was $40.
The aperture control is wonderful (the little round knob that pulls in and out in the left of the picture.) There is an electrical lead that gets in the way a bit, but I can handle that.
But does it take good images?
I'm working on that - here is a first pass (after a picture of the lens)