The FPS has been the subject of an ongoing pricing controversy, with Activision wishing to charge £54.99 for the title.
However, according to MCV, retailers such as Sainsbury's are offering the game for as little as £26, while HMV are letting it go for £9.99 if Tekken 6, Uncharted 2 or Forza 3 are traded in.
Elsewhere, Asda has slapped a £32 price tag on it, with competitors Tesco selling it for £37.90, or £25 if another chart title is bought alongside it.
Game and Blockbuster are also offering trade-in deals, with Game knocking £25 off the rrp if the original Modern Warfare is traded in, while Blockbuster will let it go for £19.99 if a selected game is swapped.
Modern Warfare 2 will be released for the PS3, 360 and PC tomorrow.