I had my house built for around $60 sq. foot if figured under-roof and $81 sq. ft if only figured for heated space. I have large porches and 30x30 garage unheated which accounts for the difference in price.
It is not fancy but practical. We have marble flooring everywhere but bedrooms and bathroom. Bedrooms have hardwood, bath has ceramic tile (marble we felt was too slippery when wet). All appliances are pro grade, windows and doors are double pane with e-rating, all interior walls are insulated to help with sound reduction.
I rough designed the floor plan then had a draftsperson draw everything to scale ($100 fee). After looking at it and some more looking at the layout, we had to reverse the whole plan to put the garage on the opposite end. We redlined all the changes and another $100 got us a fully detailed floor and roof plan. We then just sat down with the contractor to discuss details and put a contract in writing with allowances for windows and doors, appliances, HVAC, cabinets,interior trim, etc.
I know most folks wouldn't trust a builder to do this, but the guy had just finished sister-in-laws house next door and did a very good job so we were happy to do it that way. I had asked him if we needed to spec anything out and the only thing we speced was the SEER rating for the HVAC unit. Everything else was standard practice quality. We worked within the budget on most things but did about double the budget on custom cabinets and countertops but we saved a bundle on the flooring cost that offset the cabinets.
I would not recommend doing as I did unless you have extreme confidence in your contractor. Ours was a local person with good references and the payment schedule was in 3 parts based on satisfactory completion of the portions specified.
Of course land cost was not included in the house nor was the $6500 septic & $3000 lawn sprinkler system which we had put in by other contractors.