Like Square Chopper said, its a common sense thing.
Just imagine if something went wrong at 30-50 miles an hour and you hopped off your Mini, what would you wanna be wearing?!!
I went overkill last year and found a leather sportbike jacket/pants combo on Craigslist for a hundred bucks, a full face helmet for 75 bucks and bought some gloves with carbon knuckles in the closeout bin at the local cycle shop for 15 bucks. The money adds up quick, but if I happen to go sliding down the track, I could probably still go to work on Monday.
This is a really laid back FUN event, no trophies, just braggin' rights.