Well, I've had a few occasions to feel really stupid...
Passing up a Mateba Unica 6 revolver for $900.00. "Too much money"
At an antique show with my wife, passed on a minty Colt Trooper for $300.00.
Early on, passing on a Mauser "Red-9"
semiautomatic pistol for $400.00. "Who wants that thing?"
Walking past an original TDE Auto-Mag. Seller wanted $900.00.
And, one of my crown jewels of stupid:
Walked in my LGS; seeing a REALLY nice, minty Luger pistol, about 99%, in .30 Luger. Passed it up because it wasn't a 9mm. Price was $650, on consignment.
Left the store, thought about it, went back two hours later. Already sold.