hey hey,It is in china,Electricity is cheap,and you can find a place do it easy ,example Small Hydropower or small factory.This began in 2012 with some people, the cost has been recovered in April 2013 , and buy 600 cards is very easy here(because so many cards are made in china...).

Electricity is $ 0.07 / KWh, 6 * 7850 probably consumes at 900W, so one day the electricity is 2160KWh * $ 0.07 = 151.2 USD per day, Electricity is about one-third of income.