A thread was started not too long ago to discuss this very topic. If the auction you mention is sponsored by the same party as past auctions, Gthirteen answered the question (at least in part). "...if you read the fine print on the Cardas RCA Caps Auction that you are all refering to, you will see that the seller is allowing the buyer to apply the amount paid towards future Cardas purchases of over $200. So, if I bid and paid $40 for the Cardas Caps, I would get that $40 back, if I decided to purchase some Cardas products from them in the future. So, that's perhaps at least part of the reason. Cheers." So, it appears that at least some buyers may be purchasing these caps above retail as a kind of deposit for future purchases - in which case they become free. That isn't to say this is true for all buyers. But perhaps it explains the "trend".