Helmets are more than a marketing scam I know I tried one out last March and walked away from a serious accident. For 120 bucks you better be getting more than vinyl and plastic straps in fact you won't see that on $40 helmet go and try some out. If they are snell approved it doesn't mater if they ar $15 0r $200 the protection is the same the difference will be in weight, air ventilation and adjustment systems. There is a lot more engineering to those puppys than $.50 in Taiwan. The thin plastic and foam does what it is designed to do, protect ones head. Check out Bell they have helmets in all price ranges and a really good warranty for more info on helmets check out this site
http://www.bhsi.org/
Watch for sales at the online bike store but I also got a good deal on a helmet a couple of years ago at overstock.com they don't always have them so you might want to check periodically