the micro transactions can only work for you if you already have those levels unlocked to purchase those cars/parts. if not. it wont matter what you've paid for.
so basically its like this. if you can get car A B and C at level 1, and part A, B, and C at level 1. you can pay for car and parts A B and C. you can also buy car D and part A for that next level car.
problem is. you cant use car D nor can you use part A made for Car D, until you're at the level where CAR D and part A for Car D is accessible.
So its not to bad with the micro trans.
The reason for microtransactions is obviously a money grab for these companies. but there's also a gamer side to it that no one talks about.
It's for old head gamers with kids, wives, and students who actually hit the books hard to the point where they wont have hours upon hours of time to play daily to keep up with the rest of yall playing these games all day and all night long. So the micros usually give these guys chances to rank up their player, cars, etc much faster so they can enjoy the fullness of the game with the limited time they have to play it. The one issue with that is, we know the same dudes that play these games all day everyday are also buying out the bar and blowing their players, cars, etc up to the full max on day one with micro transactions. to get an edge on the comp. because these types will do anything to be #1 on a leader board.
Was thinking bout grabbing it
and 
when rockstar or naughtydog reissues a year old game at full price