I went through the process a few years ago. I have a two story home with 2112 square feet. I paid a guy to install the HVAC, run the ducts, etc., and the total price (Rheem system) was
about $5200. The plumbing I paid a guy to do the rough in, but then handled all of the sink/toilet/bathtubs, connections etc. from there. I think the total cost for the rough in plumbing was $2k with labor and PVC. I did the same kind of situation with the electrical, but paid a few guys to pull the wire as that can be a pain in the a$%. Then, I did all of the hookups at the service panel, attached outlets and switches, etc. This cost me in the neighborhood of $1200 plus the wire, outlets, switches. Of course, I live in an area where there are no building inspections. So, I'm not sure that the work I did myself would be legal in a more bureaucratic area. The price you were quoted seems high. Move to Alabama. It's cheaper in the South!