I just won a mint Pokemon promo Mewtwo #12, which was issued with the April 2000 issue of Nintendo Power magazine. The seller, who was subscriber to that, said in the auction copy that he'd just found this card tucked into a book (he indicated he wasn't a collector, but "couldn't just throw it away") and figured he'd put it up on eBay.
Now, tracking down the "values" of the promo cards can get a bit dicey, as my "reference retail sites" are spotty on their stock of the various promos. However, the site with the typically lowest prices has this listed for $25.00 and a web search turned up another couple of cards going for about that. My winning bid was $3.01 so this was quite the deal!
I'm frankly surprised that this didn't get more "traffic" ... when I stumbled onto it, there was just one bid, by a "0" point newbie bidder. With a few minutes to go, another bidder got in, countered by the first, but they stopped back-and-forthing at $2.50 ... I came in with $3.01 with about 45 seconds left and the second bidder upped his bid to an even $3.00 with about 30 seconds left, but, obviously, didn't have time to counter again. This was the second auction that I won today by 1¢ ... no doubt to the great frustration of the other bidders!
I typically make "uneven" bids, and vary the amount, when going up against other bidders. I know that I'll research their past wins to see how they've typically bid, so I assume that others might be going into my eBay Member Profile to see how mine have gone, and I don't want to leave them definitive answers!