Originally Posted by Loren

On the flip side, if you break your car on your first autocross run and it can't be fixed right away, you're only out $30-40. If you break your car on the first lap of your track session and can't fix it, you're out $300-400.

Autocross is a great "shakedown" step if you don't have great faith in your car. Nowhere near the stress of a track session... but if you can't make it through a few autocross runs, you WON'T make it through a session at the track! You can also reveal suspension and handling problems that you might otherwise only see "when you get in trouble" on the track.