use this https://bitclockers.com/calc
at todays rate of 103 usd
diff of 19 mill
9gh is used to account for fees of 10%
I put in 1 watt at 1 us cent for power
for the next 7 days.
btc = 1.65128314
usd = $ 170.31
I then did a 25% per month jump which is possible .
this would give a 1 week payout on the date of july 18 to 25 of $131.39
1) current difficulty is not possible. They are not hashing NOW, so current difficulty will not happen. If they plan in september, multiply current difficulty at least x4, which is the change of difficulty we had from March to this very moment. This is conservative, because as you know the ASIC manufacturers didn't even start to ship units to the consumers.
2) A 25% per month is much less than we are having. Currently we are having 25% every 10 days, which basically means that difficult doubles every 30 days. That increase cannot be sustainable long term, so just use something lower, let's accept your monthly 25% even if it's way too optimistic during a technoglogy change (GPU+FPGA -> ASIC)
So: I'm running your calculations with 80 mill difficulty (x4 the actual one) and 25% monthly increase, no electricity costs, one year timeframe:
BTC EARNED: 7.85184820
Revenue: $ 824.29
So you are actually losing money ($1,000 - $824.29 = $175.71)
7.8BTC generated in one year. Now explain me how the heck do you generate 50BTC from 7.8BTC "reinvesting" 30% of that "profit" that costed you $1,000.
Wake up, 10GH/s cost $200, not $1,000.