its just so damn expensive!
i've got an air attack and for me it's a great helmet. Try them on in person, though, and make sure it fits your head first. For road bike TTs, I use the air attack with shield, will use the air attack without shield for races on days that aren't super hot, and use the LG course for the days that are super hot. The best aero helmet right now if you're not adverse to buying specialized things is probably the Evade. Within the next year, the options will be really be opening up from others such as Bell, Kask, etc. the POC helmet actually fit my head pretty well too, but it's also pretty expensive, and I didn't need/want another helmet.