oh i forgot to add - i've been riding motocross for, oh, five years now?
My helmets have been in the $80-100 range, and they have been through quite a bit, quite a bit indeed... and I've never had a concussion or other head injury. Ended up in quite a few trees, ravines, and gravel pits, sliding across rocks, cement, hard pack and timber... but my head has never had injury. And I ride HARD. I think if you WANT to pay a lot of $$$ for a helmet, keep in mind, you're mostly paying for the brand name. Just make it dot and snell certified and you should be hunky dory.