Those prices are for the secondary market, not through bitmain.
Bitmain is selling batch 5 of the D3 miner. the first batch price was $2699… it was dropped to $1400 for subsequent batches. If you can get a D3 at cost, even for a 4th/5th batch you are a good bet to get your ROI.
i wouldnt pay secondary market prices for anything but batch 1 or 2. the difficulty by november/december is going to really cut into the profits a ton.
the graphs on Dash difficulty already alarming.