Currently 1.6THs will only earn $14 per day before electric costs and that will be substantially lower by delivery in October. It's not much better than having a handful of USB Block Erupters a year ago.
Yeah, isn't it crazy. This year is very strange: ~70 fold difficulty increase since last November, but more than 50% BTC price decrease.
I would have never guessed that this would be the case. I don't think that this dichotomy can continue much longer, but who knows.
At 100 billion difficultyis where the 1gh/w miners become uunprofitable. To me that's around the upper limit.