Best Buy is really good, well, at least when they are running their promos. Due to my wife losing her part time job this month, I knew that I was going to be short over the next few months when it came to games, dvds, and collectibles (necessities first
). So, for the heck of it, I gather about 14 old games (nothing stellar, I think Fight Night Champion was the newest one I took) and took them into the local store. I ended up getting 213 dollars in best buy credit for them (pre-purchased RAGE to get the 50% extra since I was planning on getting it anyway). While that probably doesn't seem like a lot, most of the games were bought from the local Blockbuster when they have deals, etc. Heck, I only paid 15 dollars for Need For Speed Shift 2 Unleashed, but I got 22 dollars in credit with the trade in deal. I can honestly say I made back the majority of the money I spent over the last year by trading them in. And, that money will pay for Rage, Dark Souls, Uncharted 3, and most of Battlefield 3.
I agree about trading in a game that you pay full price for - you lose way too much money that way. I try to only buy a game new at full price if it gets great word of mouth or is a legacy title (for example: after Uncharted 1 and 2, I would buy 3 Day One with no review input ... the first 2 games were that good). I do tend to experiment with lesser games when I can find them cheap used. And, those I don't mind trading in when I am done with them.