I believe Jigger's point is that AMD's card offers much better performance for the price.
OTOH we know the Polaris 10 die size is about 25% smaller than GP104, and it's not inconceivable that AMD are actually getting a decent deal on their 14nm wafers either. Plus, we don't whether RX 480 is a fully enabled Polaris 10 or not; AMD could be absorbing poor yields now in order to retain their pricing when yields improve. Plus I imagine the PCB, power delivery etc. are cheaper for a lower power card too ... all sorts of reasons why the RX 480 could be relatively cheap to produce and the GTX 1080/1070 could be more expensive.