Worth investing in to a cloud mining companies? Worth investing in to companies like hashflare.io or genesis-mining.com?

Hashflare:

During black friday there's discount - 1TH/s for 100$. Maintenance fee for 1 TH/s is 0.4$ == 0.0005 BTC. 

1 TH/s gives 85-90000 satoshi - 50000 satoshi MEF = 35000 satoshi profit (0.257809$) * 30 = 7.71$ per month, 7.71*13 ~ 100$. So, ROI is 13 months...

But profit for 1 TH/s would vary during a year. So 90000 satoshi per 1 TH/s might be even lower, right?
Yes, profit will be even lower. Hash rate has grown from 540 PH/s to 1800 PH/s in the last year. At that rate it will take much longer than 13 months for your ROI.