This is kind of a general, not commuter specific question, but WTH.

I just bought a helmet the other day, a Trek something or other. An LBS has an annual
clean-the-closets sale and I've gotten my last three helmets there because they get
very cheap in the last few hours. If it fits relatively comfortably, I buy it.

So, I've got a $15 helmet that retailed at about $40. Have I sacrificed anything? What
value is added to a $110 helmet vs. an $80 helmet or a $40 helmet? I'm only concerned
that the helmet keep my brains intact, that it's ventilation be okay, and that the strapping
system work to keep it in place, all of which this helmet seems to do. So what's the
difference between my new helmet and some helmet three times more expensive?