I used to race those cars, not the drift ones though. I had a Nitro RS4, which i burnt up the engine in twice before i got tired of it, and i still have my Yokomo MR4-TC Pro, which is hella outdated, but i have probably 1700 dollars in the car, all my equipment, the electronics, and everything. And thats not even a gas car.
As for MPH, i used to play with cars on my street, cars coming down the street, and id blow by them without much trouble, so figure mine was doing 45 or so MPH, multiply that by 10 because it was 1/10 scale.