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(prismas and similar gear are about 1BTC/TH), with maintenance fees around $0.07/kwh. (prismas use 0.7w/GH). Its pretty competitive with the alternative, but still requires certain key factors to be a positive ROI.
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Prismas are 1BTC/TH but without PSU and without shipping (and mostly import tax too). Add those and you easily can pay more than 1.3BTC/TH.
AMHash is using tubes not prismas. Those are more power hungry. So there's alot of room to lower maintenance fees (that includes power) in the future when switching to newer hardware (Gen4 maybe - 5x times lower fees). So, this MAY return positive ROI faster than buying hardware from AM directly.
EDIT: for those that hates math (me too) AMHash returned so far 10700 satoshi, Thats 8,1% of 125000 original IPO price. So selling above 115000 still makes profit.