Yes, that warning was a lot of hullabaloo. And there is close to no chance of hitting your head when autocrossing, if you don't have a rollbar/cage. In my cage-less car raced at low speeds I feel that a HJC M2000 helmet is plenty of protection. My car has a lot of factory safety features like airbags and crumple zones, and the helmet is not really a big part of the crash protection picture. So I feel that $60 was a fine amount to spend. When I start doing HPDEs at Watkins Glen in a caged car, I'll be running a 6-point harness and a $400 helmet because the safety system will be very different than the stock version. It's dangerous to try to mix and match safety components, by the way: the total system is what need to be considered. I run 4-pt harnesses that are designed to act just like a 3-point in a crash, and let the airbags do their job. This lets me stay seated tighter while racing, and keep the factory safety system intact.
Now, is a $600 helmet better than a $60? Yes. But will you ever encounter a situation where the difference could save your life, in a street car on an autocross track? I don't think so. Going full-face is a good idea if you can go off the tarmac into woods/brush/dirt, or roll the car, but only because it may save you cuts and bruises, not head trauma.
