6TH/s @ 2,500W for $5,000 (8.8 BTC) in September.

Assume delivery on September 1st. (optimistic)
Assume low electricity cost of 5c/kWh
Assume difficulty increases of 15% per period (conservative, we're currently 4 days from an estimated jump of 29%).

The result? A net loss of 0.7 BTC before turning it off in June 2015.

What am I missing here?