The kit costs about $80, the radio gear (transmitter, receiver, servo motors) about $50. It goes about 25mph (real speed, not scale). You'll also need a battery and charger. The basic setup can be had for less than $200. I raced this car at a nearby track (in Englishtown, NJ) but sadly, they just went out of business.

You can get them from hobbypeople.net, towerhobbies.com, or your local hobby shop.