Swap Meet Parts You Passed On and Later Regretted Not Buying

I have passed on alot of swap meet parts.

Just a year or so ago, a friend of mine dad passed, and let him and his mom around a dozen or so E body cudas, and alot of NOS part.
I helped him identify what I could, and bought one car off him.
He offered me his dads prized 440 six pack, shaker, 4-speed, dana, billboard, hemi orange, white gut multiple fender tag car for 20K.
I had the cash, no problem, but me and him had a good long talk, on how I was not going to rip him off for that low a price, and gave him some guidance on what to do with the car. He listened.
Yes I could have made alot of quick cash on that one, but I would not be able to sleep at night.
I knew his dad before his kid was ever born.