Sometimes when publishers bring out a new edition of a novel, they'll destroy all the old editions to ensure that anyone who wants a copy will have to buy the new version. For rarity's sake, that tends to bump up the prices for older editions, which is kind of a win-win for publishers, because while they don't get any cut of the resale value, they might get some proceeds from people who've taken advantage of the new higher price for the old edition, sold it, and still want a copy. They'll buy the new version and still have money left over.

I've overthought this.