I have several Trek helmets that I got on sale for around $25 or so. I like them because they are white, and reflect heat away from my hair-challenged dome, and they have a "dial" on the back that allows easy "fine tuning" of the fit. Two of my friends bought the same helmet after I "raved" about mine, and they are both very pleased with theirs.

I have only bought one "mega-buck" helmet over the years. It is not as comfortable as the Trek helmet although it does look very spiffy.

I have noticed that when someone with lots of hair is using a helmet with zillions of ventilation holes, I can see their hair up against, and in, the vents. If a helmet fits in such a way as to put your scalp or hair directly against the vents, it is hard to see how much air circulation would occur. On my head, just lots of little sunburn spots would appear. So, I go with white or silver helmets and get the "cooling" effect of reflection, rather than hope for much air circulation.