This is scary:
Antminer s9
13.th/s
1300w
time to generate 1 BTC with 13.5th/s 175 days
daily power cost at 0.06 cent rate, 1.87 US/day
175 day x 1.87USD =
only 327.25USD power cost to generate one BTC!!!!
Cost of 327USD would be fine at rates like 700-1000USD but hashrate is atleast 3 times too small to support current 2200USD price.
Hashrate has no time to correct this, price will.
But Hashrate isnt lineal, the best way is buy high number and sell before lost the advantage