GameStop UK has an interesting trade-in offer that will give consumers across the pond Modern Warfare 3 for 0.99p. All they have to do is buy Battlefield 3 before October 27, then buy Modern Warfare 3 before midnight on November 7. If consumers who bought Battlefield 3 send it back to GameStop UK before November 18, their GameStop accounts will be refunded for MW3 minus £0.99.
Activision increased the RRP of its Call of Duty games to £54.99 with the release of Modern Warfare 2. Normal games sell for RRP £49.99, and most shops usually knock at least £10 off of that. This is precisely why Modern Warfare 3 costs £41.97 at GameStop while Battlefield 3 costs £36.97.
You can get precise instructions on the trade-in at GameStop UK. Some might consider this promotion trolling on the part of GameStop UK. I suppose it might seem like that if you are a hardcore fan of the Battlefield series...