Well, I can't compete with most of these stories.
But mine is interesting in that it was pretty recent. In March 2020 I picked up this 1952 Bowman Minoso rookie on ebay for $8.95 with free shipping (there aren't any creases or marks, so probably a solid VG/EX to maybe EX). That was pretty cheap, but honestly not too much lower than what the average price was at the time. Anyone currently shopping for Minoso rookies knows this card would sell for 10x to 20x that today. He was very overlooked prior to his HOF induction.
Granted, that was literally right before the great baseball card price boom of 2020...but just goes to show you we don't have to time travel back to the 80's to get some good deals....there are probably thousands of overlooked cards sitting on eBay right now that likely won't be overlooked in a few years.
minoso.JPG