I want to install a in wall tank with a wall mount toilet. How much am I going to spend for a plumber to install the tank in the wall and the toilet bowl to the wall?

Is this in Calcutta, Kabul, Manhattan or Malibu.

Yes, it is on the expensive side. The drain outlet and vent need to be reworked, same goes with water inlet. Wall has to be re-framed to accept the toilet frame. After plumber leaves, you will have to patch up the wall and paint it to match the rest of the bathroom.

In my area, such installation goes little over $2K ( labor only / on raised foundation ) and about thousand dollar more when installed on slab (labor only ). You supply the frame, toilet, carpentry services and take care of the final wall repair costs.

In new construction, such installation may be less expensive as it falls under "per fixture" price category, which is a set price for new plumbing fixtures in given project, regardless of if it is floor mounted toilet or wall-hung.

Hope that helps

Milo