I used to work in an electronics store and we used to sell remote control cars, and the fastest ones cost around $250 not including the rechargable batteries. Some of them would cost $400 once you had all of the stuff.

When my son turned eight, he wanted to use his accumulated birthday money to buy himself a remote control. I didn't take him to my old electronics store, I took him to the professional hobby store where they sell the huge fuel-powered cars and helicopters and other Dad-Essentials.

These joints are super cool, and their cars are phenomomal. But they also have entry-level cars an eight-year-old. For $250 we got a fully assembled car with batteries and charger for less than $250. The car is infinitely stronger and faster the more expensive model from the normal retailers nd the best part is that the hobby store keeps a complete range of parts for the cars should anything break. The cars you get from normal retailers are made from brittle plastic and you can forget about getting parts for it. 

The bad thing about shopping in a hobby store is that you will soon feel a need to puchase a remote control hovercraft or helicopter. These will quickly consume any money you originally saved.