Need for Speed Pro Street not even on store shelves and there is all ready DLC on XBLM?

There are three or four car packs. Each cost 500 points. This seems really strange considering the game doesn't even hit store shelves until the 15th. Even Gamestop shows this as the ship date. To say this is a little early is an understatement. Also it is unclear if these packs are unlocks from the game like in Need for Speed Carbon or if they are additional cars added to the game through DLC. Problem with either thing is that if they were ready to ship DLC before the game even comes out, then why isn't it in the game? Heaven forbid they are unlocks, because that would mean that just like in Need for Speed Carbon you are paying to make progress. Which isn't playing a game, it's paying to cheat.