IF.
I wouldn't mind paying that much money for an UNLOCKED iPhone, but when you see people selling LOCKED iPhones at unlocked prices, it should be a red flag. Sure, it's what the market dictates for this product, but hell, I hate flippers. Especially the people who bought iPhones when they just came out for the sole purpose of selling them at exorbitant prices.
I could easily sell my locked iPhone 6+ right now for $800, keep my AT&T contract, and use that money to buy an unlocked phone. But I'd feel a little guilty knowing that I paid only $299.