I've posted this story before, but I always like a new opportunity to trot it out again:
Biggest thrill was in the early 1980s, wandering through a used book fair and spying a cardboard box of comics under a seller's table. Asked if I could look through them, and my heart almost stopped when I found FF #2 in (what I now know to be) VF condition. Kept flipping and I think my heart DID stop when I saw the next book: FF #1, again in VF shape.
I made sure no one else saw the books, and I quietly and calmly asked the guy what he wanted for them. He obviously knew they were worth something, but had no idea how much, because he said $50. I asked him, "each?!", and he said "for both". I gave $50 cash and got the heck out of there as fast as possible!