Actually this estimate is incorrect. If you look carefully, the first mining month is estimated as having a diff of 293 million(!) Our units will start shipping on October 2nd, when we will still obviously be at the current difficulty 149 million.
We'll be at (or about-to-be-at) 200 million when they arrive a couple of days later though, and you had to fiddle the electricty rate down to show it getting an ROI :p
This is a big flaw of the mining.thegenesisblock.com calculator...
It also incorrectly assumes the difficulty will remain constant for a whole month - which it never will - so (putting aside the %age growth will eventually slow down argument) generally it paints a far-too-optimistic picture !
Sadly though with the power consumption, even though it's a great design and engineering feat, and major kudos for actually having a product rather than pre-ordered vapourware, anything over 8BTC is unlikely to ever break even for the majority of potential clients.