It's funny how people still prefer the units over their money back. I suggest some math and taking a look at the difficulty development over the past months as a comparison.
The calculator over at
http://mining.thegenesisblock.com/, while informative, is vastly overrated. The difficulty will start tapering off around January, not scream up to the insane levels thys currently show. While 1 billion difficulty is possible, 30 billion in 12 months is like expecting BTC to hit $1,000,000.