Well not really half or anything... Depending on running sales I have seen 1070's as cheap as 349.99 in just the past couple of weeks. (not the mini's too) It doesn't really matter because I would never even bother mining ETH with an Nvidia card anyways. I also think that for resale value the 1070, 1080, and 1080 TI are by far superior to the 4xx/5xx GPU's. Nvidia can also mine many different algorithms profitably and they are less of a hassle to deal with as you don't change the bios and there are overall less driver issues. That is just my opinion but I started out mining AMD but have recently transitioned to Nvidia.