At $0.02 per KW, you are profiting on average $320.00 per month for each S7
You have to recoup your initial "investment" (purchase price of hardware + psu) before you see any profit. Even with 2 cent power (which is rare in and of itself) you won't see profit for over a year. That's why I mention ROI even at low power rates. New hardware purchased at retail price just doesn't make any sense right now.