hardware cost is a 1 time cost, electricity cost is negligble 90k for the whole year, storage cost is 0, maintenance is 0(wtf lol most people don't know how to maintain these things).
but yeah total profits per year should be 12-18 million uSD
I've had to replace worn out GPU's and MB's a couple times this year so far. So no, heardware cost isn't a 1 time cost. Go see those mining profit calculators; it'll show you that the on average a GPU takes around 3-4 month to recoup the hardware costs alone, and barely factoring the electricity costs in. And you'll have to factor in that ASIC's and FPGA's are taking the market, and the rise in difficulty. Electricity costs are not negligible unless you use ASIC's or FPGA's.
Maintenance is the amount of time spent to set those machines up and keep it going, and time is money. Mining was wildly profitable last year when the prices was $20~.
