I didn't drive, but I did crew for a friend that bought and open wheel modified and decided to go racing at our local track. He picked up pretty cheapr ($2k or less from what I remember), and it was one of the fastest classes there. It was a mid pack car however, but he still had a blast. One thing not mentioned here, is that you can also pick up local sponsorship somewhat easy to help pay the bills. In the end it was much cheaper than road racing and you could race and stay at home.