FWIW a member of this forum found a Pratt D1-4 6" 3J lathe chuck for sale near him. [for those not in the know, these were amongst some of the best chucks available in the 1970s] He offered the deal to forum members, and to to pick it up. Of course I quickly agreed. He could have bought it and resold it at 2-3X what he paid. Like new condition, 2 sets of jaws, original key, no rust, essentially unused.
When I came over to pick it up I had forgotten the price, and tried to give him 50% more than he paid. He told me the right price, even after housing it (and moving it a lot) for nearly a year.
This is the kind of paying it forward that I try to do also.
If I think I need to get more (under exceptional circumstances), then I will state my purchased price, and what I'd like to get for it.