IT will be interesting to watch this progression also as i have a good bit of capacity at GM.
however i am in the 4%+ affiliate range and work with a group of affiliates to always get the maximum discount.

if you buy in quantity (5Th/s+) and get a good referral you can get as low as $130 per TH/s buys.....

the S9s on the market run $150-$170 per Th/s before PSU+ Electricity and man hours.

SO the only scenario i can see losing here is if GM goes under....especially if you have a means to invest from a corporate expense situation.

So i will be following this.  (just my 2cents)