All of the valuable stamps are already discovered
This one did have me fooled when I was a kid. I received large boxes of mostly kiloware and a small US catalog. I was deluded into thinking I would eventually find something like a 1502a if I just went through enough stuff.
Little did I realize, it was one guy who found one sheet, hoarded it. Then made up a fake initial price, hocked a few at auction to keep a business running, advertised one at some ridiculous price that I would savor over and kept the rest under lock and key until the advertised one sold and made the next one available. Or a dealer would drop dead and his holdings would come to market. That was the reality.
Now I believe I collect these somewhat because of that inability to have found them when I was young. I don't know the root cause for the bug.