I'd assume the 480/X will launch at $200-220 and $250-280. It could be less but based on AMD's claim that they want VR capable cards under $300 they'll most likely stay closer to $300 for the top Polaris 10 card.
390/970 performance will be $200ish, Furyish performance would be $300ish.
There is no way to sell cards otherwise due to the older cards getting price cuts to that location anyway. 290 have sold for $200ish once 390 came out and these chips are cheaper for them to make. Same with fury, its a pricey chip. I wouldn't be surprised for the big Polaris to hit its speeds if they want to price something @ $300-350 range.
Top end card price is dropping regardless, they can't keep selling fury @ $550+ once 1080 launches, so those cards will either drop to $400ish or just be outright replaced with a Polaris card.
They are not only trying to bring VR to more people, but also have to compete against old cards that will be getting replaced.