Polaris 10 just isn't competing in the same market place as GP104 cards, that is why Nvidia have GP106 cards coming soon.Seems like a sound strategy to me. NVIDIA are definitely presenting them with an opportunity there.
Plus the fact that the 1070 is only $50 more than the 970, inflation alone takes care of about $15-18 of that difference. I expect nvidia have do e their homework and know what price will by the boat the load, just like the 970. And the if they misread the market there is a simple fix, knock off $50 and they should see huge sales like the 970 did.