Doesn't make sense even with your explanation. Sell a lv 90, Blizzard gains money and you save time. Terminating a lv 90 does nothing for Blizzard short of creating work.
http://us.battle.net/wow/en/forum/to...261?page=8#154Originally Posted by Blizzard Entertainment
If you don't like your 8-9 90s you've leveled, find a way to like them. Try different specs, PvP, PvE, whatever works. Otherwise, they'll just sit there and become bank toons/gatherer toons.
That is one thing I enjoy about EVE, farming and trading in-game to buy game time
Blizzard could not possibly make it work, look at what the AH/GAH did to Diablo III.