As to electricity costs, I was personally running a small 10 kW GPU farm at $.02/kWh back in 2011 in Douglas County, Washington where most Public Utility Districts are basically non-profits due to historical reasons in the region. Most smart large-scale miners are paying $0.05/kWh or less. If not, they are dumb and go bankrupt like KnCMiner did 2 weeks ago.
So 1 TH/s of Avalon 6 gear costs $0.36/day, however at $0.05/kWh it mines $1.74/day right now (or $1.00/day 2 weeks ago when BTC was around $400). Certainly profitable.
There are some capex issues with scaling up that farm, and I bet you aren't costing your own time in there. But, I hear you that it's possible, and it's interesting to hear that $.05 fully loaded is possible outside of government subsidy situations.
28nm gear is not profitable right now as far as I know, or it just got reprofitable a day or two ago.
28nm parts give us something like .51 W / GH = 12 kwh per day per TH. That power quote may be at the wall, but probably it's a bit more than that.
1 TH = $1.74/day right now, pre-halving, soon to be $0.85
Fully loaded costs of energy and datacenter: $.06 - $.12 / kwh = costs $.75 - $1.44 day.
So, at $400 coins, those rigs were a loss unless you were in very cheap energy and labor markets, and then just barely making some cash.
At $670, they are making a bit of money again, if you kept them around and didn't decomm them in favor of 16nm parts.
I think the end of the road has been not just in sight but essentially here for 28nm parts for the last couple of months. But, I did oversee a multi-megawatt mining business that mined unprofitably for a number of months to finish out our datacenter lease, so that is also a possibility here, and might explain why 28nm miners won't go away right this second.
That said, if you know of ways to get fully loaded costs down into the $.02 -$.04/kwh, I would really like to learn more about that - I'd LOVE to be wrong about this.