Yup, and is dropping each day due to the Bitcoin price increases and Scrypt alt-coin reduces. So I believe it is no longer a good estimate. Maybe about 0.05BTC/day now
at a btc price of 180 that's 9 dollars per day or roughly the same 270 per every 30 days if you were on the most profitable coin and not necessesarily autoselling for the market price. I would be on a limit order scheme if I were you and you could likely see more than just .05 btc a day. Im doing 25 GH at like .05 btc a day so I don't know where those numbers came from.
Are you mining BTC directly?