And when I checked your numbers, it looks like you're only factoring the electricity costs, and nothing for depreciation.
It`s the right way calculation. All my equipment costs had been calculated until revenues exceeded costs. Now there is now depreciation, it was calculated before.
Even if GPU-ASIC - break down - it doesn`t make a problem. it worked hard and paid off itself.
It would only be the right way if the cards were worth nothing. However I suspect they are worth something, and the more you use them and the longer you wait, they are worth less and less.