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I doubt cost is the issue. If it's proven to make a difference, then any sane person would spend the extra money. If a helmet is Snell approved, it's Snell approved. If there is some other data to strongly suggest that one model of helmet is a problem, then it's smart to ban it. I just haven't seen any of that data.
Personally, I ride in an HJC AC-11 because it:
1. Is Snell approved for racing
2. fits my head
and
3. happened to be priced right.