One cool find I made was when I bought the Hausermann aluminum deck "Cocktail" on eBay in around 1998.
It's a very cool and desirable deck, with Art Deco-themed courts. (NOT Art Nouveau).
I outbid the competition, getting the deck for around $135.
When it came in the mail, I was surprised to find that it was a Patience-sized deck (around 1.75" x 2.5"), something that was not mentioned in the auction description.
When I mentioned this to one of the others who had been bidding (in those days, you could see who was bidding on something), word quickly traveled, and everyone wanted to see photos/scans - none of us even knew there was a patience-sized version of the deck!
Had the seller mentioned the deck's size in the auction listing, it would easily have gone for $500 or more!
I recently saw an eBay listing for the much less-rare standard-sized version of the deck, and the starting bid was over $600!
Here is a current auction of (I think) the standard-sized version:
CLICK TO VIEW LISTING