Subsidy or not the cost is real. At this point there is no economic demand for an 8TH network. Maybe not even enough for a 1 TH network. The current network (at a guesstimate of 2MH/W, $0.10 per kWh and $1 per MH capital cost) consumes nearly $10,000 daily in electrical power and burns through another $1000 in depreciating hardware). That simply isn't sustainable given the tiny amount of economic activity actually occurring.
Since we're bringing things back from the dead:
Assuming 200,000 btc trade hands at lets say an average of $10, (just at mtgox) thats 2 million per day, with mining costs of 11,000 per day. Is this not a favourable ratio?