Since that's a book remainder outlet, that means it was dumped by one of the big book stores (BN, Borders, etc). I would imagine that they have a policy of clearing out the warehouse after a certain period.
Wonder if their policy is to clear out books older than 9 months old. The 4E D&D titles listed on that EBay store (bookoutlet2) only goes up to Primal Power from October 2009.