Picked random game from gamespot used list, Battlefield, that I instantly recognized as a EA title.
http://www.gamestop.com/Catalog/ProductDetails.aspx?product_id=73884
Only a $10 difference between new and old. If you have to pay an additional $10 to use it, I'd rather just buy new.
Gamestop is setting the price for used games at what people are willing to pay. If people have to pay $10 more to EA to play the game, that means that Gamestop will likely have to charge $10 less for used games. They will of course give people less for games they wish to sell back, but the margins on used games for retailers like Gamestop are going to shrink some.
This will make for unhappy customers and unhappy games retailers that sell used games.