I've been all over the manufacturers websites and, aside from the number of vents, I can't find any difference between the cheap helmets and the high end models.

Quite honestly I think they've identified their markets and priced helmets to fit what they believe cyclists are willing to spend. Those who want a basic helmet can get one for $20 to $40. Those who want something with more ventilation, or don't want a "cheap" helmet can pay in the $50 to $100 range. Of course if you want a helmet like Lance, you get to pay for that too. They already know parents aren't going to pay a whole lot of a helmet that could be outgrown in a few months.

My $5 flea market special has 9 non-functional vents. The advantage is, it's warmer in the winter and I don't get the sound of air rushing through the vents

Stacy