The rise of prices will be logical if Primitive Shaders activation in drivers, and proper drivers will bring significant increase in performance. Otherwise it would be absolutely stupid move by AMD. NOBODY is that incompetent.
The fact that they are willing to raise the price some time after the launch after the release suggest that currently we get unfinished product at a discount, if this theory is true.
However, Gibbo was wrong before about mining performance of Vega. On the other hand, if Primitive Shaders feature is bringing large uplift in performance that would justify the price hike - then maybe Mining performance is still crippled by drivers?
Theoretically this makes sense.