There are fewer than 20 of the 71 Winner's set currently known. Since it was part of a Topps contest, as I recall, at most there would be 25. I assume there was no cap on the 79 offer.
I think the reason the 71s do show up on ebay from time to time is that the cards are labeled on the front as a Topps product. Since the 79s were not labeled as Topps on either the front or the back, they would seem less likely to show up in auctions unless they involved an actual MLB player.
I once tried to do a saved search for "1979 Tradin cards" but ebay always changed int to "1979 Trading Cards", and that turns up all kids of unhelpful stuff
