I started with a $25 Bell helmet from Walmart. Thought I'd upgrade, when I found a normally-$99 Bell helmet on sale online for $54. Some upgrade! The more expensive helmet weighs an ounce more than the cheap one! Ventilation is supposed to be better (I'll let you know when it gets over 100*...as of now, I can't tell the difference)- but all I've noticed so far, is that the "upgrade" seems to let more bugs in.

I gotta remember to stick to my motto: The "best" is usually the minimum necessary to do any particular job without it being a total piece of crap.