Sigma DP1 Merrill also for $799
I get the feeling that producing these cameras is a hobby for someone at Sigma, and as long as they can generate enough revenue to cover the R&D and manufacturing costs, they are satisfied.
They will never be mass market items so the revenue from each camera needs to cover a significant portion of the development costs. If they are selling enough at these prices there is no reason for them to reduce them further.
Many users are frustrated by the unwillingness of Sigma to fix some of the useability issues of the cameras and the software, but if they only sell 20 or 30 thousand units there is not much money available to make these changes.