384Mhash for ~$2100.
10 months to break even at 6000 difficulty $.10 power
25+ to break even at 12k diff and $.10 power.
(according to Coin Warz calculator)

I'm sure your numbers are right. But I think you are assuming there will be no virtuous cycle provided by a more secure blockchain. A Chinese company committed time and people and money to design, tapeout, manufacture, characterize, and bring into production an IC that is dedicated to mining X11 secured blockchains. This is capital intensive work. This is not rolleyes. This is a vote of confidence in the future of DASH.