In the early 80s, I had a small computer business; actually, my younger brother live in the same dorm as Michael Dell and told me about him and how he was building and selling clones to other UT students, ordering parts from a magazine called "Computer Shopper". I got into building and selling them, too. Then, a friend asked if I'd trade him a complete system for an old "limey" bike. I built a complete computer with drives, monitor, mouse, printer, all the cables, even a high speed modem (all the rage back then), and set it up in his living room. I taught him how to operate it, showed him how to save to disc, print stuff, everything. That computer was worth $3,000 at the time (high end PC system complete); present value would be the equivalent of about $5K. He didn't lift a finger to help me drag the scruffy old Norton out from under a bunch of old lumber, tree limbs, car tires and what-not, out behind his garage. I even loaded it by myself.
So, AFTER I cleaned it up, re-wired the points to get it to fire, cleaned up the brakes and got it running, he calls me up and tells me to bring his bike back and take the computer; he didn't like it (no other reason). Since I had a big public sealed bid about to be awarded, the last thing I needed was any kind of bad rep. I took his RUNNING, CLEAN bike back to him and collected my computer which he had made a mess of.
I won the bid for 30 computers which basically launched a 15-year successful business that helped me build my motorcycle collection up to 50 bikes, 20+ runners (a half-dozen total restorations). But I would always remember that sour deal. The bike was eventually bought by the guy I bought it from, who had a mutual friend start to "restore" it (to a Production Racer replica, which the other guy claimed was more valuable); our mutual friend died unexpectedly, and the guy I bought it from had to BUY IT from his druggie widow to get it back before she sold it for scrap.
4 years of pestering him, and I finally wore him down.