A lot depends on what has to be done to access where the lines will be run. Takes longer if he has to drill holes in studs etc. If the house is new construction, the cost would be lower as it would be done before walls are covered with drywall. Then a standard "per fixture" formula could be used. Local wages and material cost can boost the cost and since we are from all over, geographically, estimating your cost would be difficult.
If you have never made a mistake, you haven't done much.