mdd1963 :
...now that Nvidia seems stubbornly determined to make $350 the new 'mid range'...
Another way to consider it is that Nvidia shifted their product names for the RTX series, which makes the 2060 more a successor to the 1070. Looking at it that way, it's more a case of underwhelming performance gains from one generation to the next than an increase in price. The 2060 launched for a little less than the 1070 did back in 2016, and has some new hardware features that are as yet mostly unutilized, but on average, it tends to only be around 15-20% faster in current games, and has less VRAM which could potentially impact performance in the future. In all, those are pretty mediocre gains considering over 2 1/2 years have passed since the 1070 debuted.
There's another card that's supposed to be coming out very soon though, which should be a somewhat more direct successor to the 1060 6GB. The 1660 Ti will apparently lack the RTX features found in the new 20-series, and I suspect it's performance may fall a bit below that of a 1070. It should be a decent amount faster than an RX 580 or GTX 1060, but it remains to be seen how it will be priced. At $250 it could be a good value, though I suspect it may end up closer to $300, which depending on how it performs relative to a 1070 might not be so great.
And while AMD will have new mid-range cards coming eventually, there have recently been some rumors that they might have been pushed back to a fall release, rather than a summer release that many had been expecting. If that's the case, then Nvidia might not have much incentive to price their new cards all that competitively.