Blame Infinity Ward for that, IllegalPaladin, not Steam.
If you find the PC version of COD4 cheaper in stores it's because they're taking a bigger hit to get the games off the shelves.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )