Not quite the same as Forza. As I understand it in Forza you could pay real money for a car, but you still wouldn't be able to use the car until you spent in game credits(which you can also pay real money for) to unlock it?
That's what I've gathered anyway, if I'm wrong I apologize.
You're mistaken.
In Forza, you can buy "tokens" which can be used to unlock cars in lieu of grinding for the regular in-game currency they would usually require.
Not really any different to what DriveClub is apparently doing, except DriveClub cuts out the middleman currency item in favour of just letting you buy your way to the car directly (kinda like the difference between XBL and PSN when you had to buy everything on Live with MS Points vs PSN just using real currency).
What you're probably thinking of is the way DLC car packs worked, which was that you bought the DLC, which just made the cars available to purchase/unlock in-game via the usual methods (grind for credits/pay money for tokens). That's actually how things have generally worked in racing games since DLC became common (previous Forza entries worked the same way, GT works like that, etc). They actually
changed that back in March, though, so that cars you've bought as DLC can be added to your garage without any additional in-game cost