A pricey bit of personal kit - yes. Compared to the price of the airplane? Peanuts.
I wonder about things like mass and volume in a cockpit where keeping one's head on a swivel is important. And I wonder about how the displayed information holds up under the dynamics of moving target, moving airplane, moving head and all that. Also, as primary display, it happens to be monochromatic - so distinguishing all the kinds of information - in a hurry seems like a challenging prospect. God bless our awesome skilled pilots.
The helmet is the "primary display" and I wonder what's left when the unthinkable - display failure - occurs. A $400,000 helmet can't really fail, though, can it? What was I thinking?