Go look here:
https://bitcoinwisdom.com/bitcoin/difficultySeems like you are losing value at with at least 15-20% per 2 weeks (Output drops by the difficult rate increase, in case exchange rate stable).
In reality output + value drops more, power price is a constant.
Antminer S1 running @ 200GH/s uses 400 Watts/hour = 9.6 kWh per day.
It produces $5.462 woth of bitcoins at todays exchange rate, going down by the diff increase every 2 weeks.
Not sure what your power price is. But assuming it is in the high end = $0.40 /kWh. Then that is 9.6 * 0.40 = $3.84 /day.
So the profit is now $5.452 - $3.84 = $1.612 per day.
In 4.5 days, the difficulty goes up by say 12%, so the output is $5.462 / 1.12 = $4.88. Minus power $3.84 = $1.04.
So at the power price, your net mining profits drops 35% in 4.5 days.
You need to calculate yourself. As it looks now, profits is getting low, and there will be lesst investment in new equipment as it will never break even at the current retail prices. Only the manufacturers will turn a profit, or those with almost free electricity.
The Antminer S1 can be pencil modded to gain a significant efficiency boost. Slower hashrate, at much lower power cost. You can get it to be twice as efficient. That is the trick they used in the S2, undervolt the chips in the S1.
But when you do the calculations, remember that 1GH/s today is 15% more worth than 1GH/s in 2 weeks.
