Traded in Bioshock 2 Rapture edition at hmv today and got £15 store credit.
The Rapture Edition was the one sold by zavvi (exclusive to them) that included the Deco Evolution artwork book. It was only £28 - £30 on the release day. (this is when i bought it)
So to get over half the money back 14 months later is very good.
Also this game sells for less than £15 on the internet.