The 570 at $140 isn't as much of a deal as people seem to think. Before the mining boom really took off you could get a 470 for $130 so it only seems like a good buy because the prices became so distorted. And here we are 2 years later paying more for something on clearance.
One of the reasons why the RX 470 got the rebrand/refresh was to raise pricing of series as they were selling near cost.
Add the 50 dollars for 8gb of gddr5, board partner margin, reseller and distributer margin, shipping logistics, board parts and there just isn't much profit if any at 140 dollars that early into the product lifecycle.
These cards were briefly experiencing an oversupply since the mining market hit early, then quickly cooled in which AMD had already ramped up production leaving an oversupply of RX 470 on the market. In addition, Nvidia was able to saturate the market during this mining spike which left the amount of potential buyers in the $200 low. The purpose of the refresh was not only to refresh the line itself but refresh pricing closer to the MSRP of the rx 470/480 to bring back the cards to much more sustainable margins.
Think about how expensive any 230 mm2 from AMD card was even a year from launch and you will realize that there has not been any that cheap, particularly when we include inflation. Combine this with die cost being at an all time high and you will realize those $140 dollar rx 470 were not making AMD any money.
Typically refreshes sell for cheaper than their older counterparts MSRP but since Polaris even at the beginning was a lower margin product than typical if we take into account the 14nm finfet cost(cost per transistor did not drop much as cost per mm of die nearly doubled), that 40-60 dollar price drop was all the margin of the rx 470.