I don't understand - 4Thps for $10000 vs 3 Thps for $11000 ? How much do you think electricity costs will be?
Think about it, 3TH for
$11,000 for 5 years = 3kw * 24hr * 365 days * 5 years * 10-cent kWh =
$13,140 for electricity alone =
-$2,140 (loss) for PBMining?
Yes, loss. If difficulty continues to increase by 20% per retarget, then after 6 months it will earn about 5% of what it was earning. After a year, it will earn about 0.2% of what it did on it's first day.
So you have 5 years of not paying electricity. For 4 of those you wont be earning anything significant anyway.