Alright, one more scenario, more extreme:

Let's assume $12/BTC, $0.25/kwh power cost, and 1000 TH network hashrate after reward halving.

Hypothetical device that does 60 GH, costs $1300, and uses 60W:
$100K buys about 4600 GH of hardware which will use about 4.6kW of power and earn about $5980 per month, minus about $830 for power, for 5.15% monthly ROI.

Hypothetical device that does 54 GH, costs $1070, and uses 405W:
$100K buys about 5100 GH of hardware which will use about 38kW of power and earn about $6630 per month, minus about $6885 for power, for -0.26% monthly ROI. Uh oh.

Hypothetical device that does 54 GH, costs $1070, and uses 120W:
$100K buys about 5100 GH of hardware which will use about 11kW of power and earn about $6630 per month, minus about $2040 for power, for 4.59% monthly ROI.

But someone with $100K to invest, ought to find a better place to setup than where power costs $0.25/kwh.

And if ~5% monthly ROI were attractive to professional miners, why has mining been historically much more profitable than that, except when the exchange rate fell toward $2? I think 10-20% monthly ROI will continue for the next year or so at least. Though a price war among mining devices could really screw ROI up.