Hazarding a guess, that AMD saw that the RX480/580s were still selling at a ridiculous price & thought "Hey, we should up the price of the Vega. Can't be selling them at barely more than those are selling at".
Can't blame them for cashing in when folk would most likely still grab them, even if it's only miners.
Personally, I was looking forward to seeing what Vega could do & it's not a bad card. It's just a bad price. I know 1080s sold for a lot more before, but you can grab some of them cheaper now, so AMD will have to hope that those that prefer AMD will still prefer them...
For me, I'll stick with my (pre-miner price) RX480 & see where things go in a year or two.