This whole LE copy is very questionable. I pre-ordered because of the LE content. However.., EVERY SINGLE copy I've seen on the shelves (at my local game and department stores) are the Limited Edition.
At EVERY GameStop in my area that carries it has the LE on the shelf. I asked my local GS manager if anyone didn't pick up their pre-orders (which would be a good reason to find the LE on the shelves).., but ALL pre-ordered copies were picked up. All the copies they keep getting in are the LE.
What I honestly think has happened here is EA/SMS pulled a fast one to boost the sales of pre-orders. They just neglected to tell everyone that the LE would also be available to consumers who did not pre-order. We'll probably eventually see a standard version.., but all the copies being shipped in my area are the LE version.
Anyways to the OP.., you have to redeem your LE code to get the extra cars and events. Then when you go into the car lot you'll find those three vehicles there with a purchase price of $0