From the perspective of a UK flyer, $3500 for a return ticket over the Atlantic in business class looks fairly cheap. Last time i checked (with one-month advance), I was quoted 4500+ GBP.
Regardless, you don't throw away your headset after a flight, obviously, so even if the ticket were half the price you'd still come out ahead after two or three trips.
This said, headsets like AVP improve the flying experience but don't magically solve it: they are still too heavy and uncomfortable to wear for more than 1-2 hours. That's why I'm betting on the more lightweight (and cheaper) sunglass-like products to actually win that market.
It's not like there's much reason to care about comforts on short flights. Anyone can tolerate economy for an hour and you'd probably not get out your VR headset for a short hop either.