Hey, thanks for your post!
GPUs aren't viable for Massdrop because the profit margins are so low. When Sennheiser sells HD800s they're probably making at-least 50% profits (they sell for $1500, I know they don't cost $750 to manufacture).
I've seen the dealer price sheets for Nvidia Direct, EVGA, PNY, and their margins are terrible. Newegg makes 3% on average when you buy a graphics card. Those big discounts you see are loss leaders where the company is intentionally losing money to make you a customer based on their theories about your possible lifetime purchases.
Massdrop works well for things with inflated margins, not for thing with highly complicated manufacturing manufacturing processes.