Please correct me if I wrong but for 600w power supply the monthly cost will be ~$50 (cost of electricity is 12 cents per Kilo-Watt hour in my area).
(0.530 KW * 720 hours * 12 cents per KW/h) = 4579.2 cents = $45.79 / month!
The cost to run the PC 24/7 under the Reasonable Load Power Consumption is:
(0.636 KW * 720 hours * 12 cents per KW/h) = 5495 cents = $54.95 / month!
(Calculations from site http://www.overclockers.com/how-much-does-it-cost-to-run-your-pc/ )
So my break even point is ~$1.5 per day, but currently I make ~$5 per day with my gtx970 so it's profitable rigth?