Many factors go into the cost of building a house.
Location: in a large city? Suburbs? rural?
Type of construction: brick veneer, wood siding, one story/two story, basement or slab foundation, ceiling height, floor finish, number of baths, fireplace, garage, type of heating, etc.
Extras: cost of land included? septic system? water well? cost of plans, permits, inspections, interest on money during construction, builders profit, exterior items like driveways, patios, sprinkler systems.
For this reason, you need to know what is included if you look at costs for existing new houses.
Your house could cost as little as $50 a square foot to $200 a square foot. Twelve years ago when we decided to build a new house, we talked with several builders and got ball park estimates for the house we wanted to build. We found many builders happy to give a quick estimate. Once we decided to build, we chose a builder and he made a more detailed estimate but even it turned out to be low by about 20%.