Eh, it's hardly surprising at this point. PD know that at GT5's age if they release all the cars in one go a lot of people will just grab them then put GT5 back on the shelf. This way people who don't play often have to remember to get their new prize cars every so often, so GT5 is always in the back of their mind when they think about playing a game... Or it's a lot simpler than that and they know that people will drive a car for a bit, get bored again and play something else. Stretching that over two months means it looks like many, many more people are playing the game for an extended period of time even if it is only for 10 minutes each time a car is released, so PD can turn to Sony and say 'look, LOOK! Two years on and people are STILL playing GT5 en masse, give us way more money (and time) for GT6!'
That's just how I see it. I have to admit this approach will certainly work on me, I just hope there's some properly meaty DLC planned for the months after and not another five car pack.
