Depends on the quality of your materials, but in the higher end consumer printers, they cost about 400-600$. So selling them for 1200-1800 is quite normal considering you need to provide support, extra R&D, etc. Most electronic producs have similar margins.
A robotic arm for printing works, but for cnc milling… There are some forces at work there. I don’t think you would get much of precision in that configuration. And the complexity would certanly drive the cost up very high.