Friends,
We are generally all forgetting something very important when it comes to bitcoin mining profitability...
I was looking at ebay last night, considering buying some Block Eruptors... I was busily plugging away at the profitability calculator to establish realistically what the ROI might be with these things, but what follows applies to all mining hardware. For reference, I use the
http://www.bitcoinx.com/profit/ profitability calculator because it allows me a few options to fiddle with.
In the "Profitability decline per year" section I put 0.05, because I think its rational to expect the network to grow by 20x within the next 12 months (to approx 10,000TH)
I also decided to use the least power efficient hardware for this exercise, both because this is the conservative approach, but also because I could have block eruptors delivered by friday. So we are talking about 7.4w/GH
So I entered a conservative 300MH and the corresponding 3w power consumption, with expensive 0.27c power costs. And about $65 cost for the Block Eruptors.
What I found is that with these numbers I mine $39 of BTC in the next 12 months, and I pay about $7 one electricity. At this point most argue, and based on the calculators figures too, it costs more in power than you earn in BTC to mine with this hardware. This means you don't get ROI ever.
However the key factor we are all forgetting is that the price of bitcoin will inevitably continue to rise. We are averaging 1000% every 12 months in BTC price rises.
If bitcoin goes up to $210 instead of $110, then even these devices get ROI in 262 days. If BTC goes up to $410, thats ROI in 72 days.
So - currently a single USB block eruptor will generate about $10/month with power costs of about 60 cents. I feel it's fair to assume that hardware will remain profitable for at least twice as long as a calculator using profitability decline per year of 0.05 suggests due specifically to BTC price increases.
And this, friends, makes all the difference.