I don't think the goal of having 500 cars in game is so we can catch 'em all, though some of us will try. The variety means you're bound to find something you'll like in each class. Personally, I don't have too much of a problem with the game economy. Cars are priced realistically, as are most parts. To be fair, I have the game on its absolute hardest setting most of the time, so I'm earning twice as much money. Also, I find that the prize cars I'm winning are often quite competitive, so I usually use those to win races, rather than buying something else. Finally, the upgrades I choose usually aren't too expensive. I'll get better tires, a better suspension, and strip the car to lighten it. That's usually it.
Don't forget to check the Auction House. There are often deals to be had there.
