My guess for the 1080 based one is they put normal gddr5 on it instead of 5x and that gives it a decent boost, probably not enough for 60MH/s but maybe mid 40s.
@OP I agree that they don't understand what the market wants. I would be willing to buy mining only cards if they had a better price/performance ratio or some other special feature, the $350 1080 one is good if it actually gets 60MH/s but the rumored $200 for the 1060 based one isn't any savings since it isn't supposed to be faster. Better binned memory for faster overclocks, better warranty, (not the rumored 3 months) cooling/power solution built around 24/7 operation, cram 2-4 gpu die on a single board, AMD has done this before but not Nvidia. Custom BIOS for lower power usage.
Rumor is the 1080 variant mining GPU will have GDDR5X with a 1080 class GPU.
I don't see 60mh out of any of this but I could see 30-35 if they really engineered something unique...
In the first generation of these kinds of cards though, I don't see engineering coming out of them. I see them trying to repackage the scraps and sell them as "mining cards" -- specifically hardware that wouldn't normally pass their QC process for gaming but "would probably last a few months" in the form of a mining card.