While I admit my numbers are older as i have been away from it for some years now...there are many in-depth articles that have discussed this in the past. Obviously, take it for what you will but...(this is one of the more recent in depth articles I have seen, but there are others)....
"Just how lucrative is GameStop's used games business? For every dollar of revenue from pre-owned games and consoles, the company gets 48 cents of gross profits -- that's a margin of nearly 50 percent."
http://www.gamasutra.com/php-bin/new...hp?story=23396