Things must be rough where you live if you consider $540 for a 1080 and $460 for a 1070 a great deal. You could buy two of the RX 470 4GB mining cards for $500 or the gaming RX 570 4GB cards for less than that, if you can find them and get roughly 20-30% more hashrate for the same price.
Nobody is selling the RX 470 mining cards for $250 - the NewEgg postings were mistakes, they don't even have the cards yet - and the rep I talked to was pretty sure they were NOT going to actually sell the things at MSRP or even close when they DO get them.
If you can get GTX 1070 at $400, GRAB THEM - that's bloody cheap at current pricing, and is the same ballpark they were in a month ago before the started getting impacted by the "mining caused GPU shortage".
Last time I checked NewEgg (yesterday), for example, the LOWEST they had a "in stock" GTX 1070 listed at was well over $500, and most were $600-$800 of the VERY FEW IN STOCK options they had at all.
BTW - they didn't have ANYTHING in an RX 470/480/570/580 for under $500 at all, and only 1 or 2 options under $600 - at current pricing the RX line has ZERO advantage in reaching ROI over the GTX 1070.
Trying to call those cards "$250 cards" is not valid and hasn't been for a month or two now.