Nothing IMO other than a couple of more vents or weird designs. I use a $30 GIRO I got at the LBS and prior to that had a $40 bell. Both worked just fine.

Bicycling magazine likes to advertise helmets that cost $160, super-thin lightweight inner tubes, carbon fiber water bottle cages, titanium bolts, and tons of other useless crap that no one really needs. A regular helmet from your LBS will do just fine

Make sure it fits your head securely...that's more important.