So for 280 TH if I buy 20 s9i with psu I will pay using my coupons 17990 usd, for the same amount of Th I need to buy 21 avalon 841 which will cost me 27520 including psu and 2 controllers,so even if I have 30% failure with the antminers, the price per TH is better from bitmain than from canaan.