I found that the dollars/sq. foot for thewhole house didn't give me enough detail.
I broke the estimate down into costs for foundation, framing, floor, doors & windows, roof....you get the idea. That let me spend money where it made more sense for what we wanted.
For example, slight changes to door and window specs made huge changes in the final cost. But slight changes to the framing - like doubling the insulation on the north wall, or adding soundproof board to the wall nearest the road - made almost no change to the cost.
Adding a second story almost doubles the final cost, but changing from a 4 foot perimeter foundation to an 8 foot unfinished dirt floor basement was not much money at all.
Consider asking for more detailed breakdown on the costs. My builder was surprised - and pleased - that I wanted to put some work in. Every detail decision I make ends up making his work easier.
rScotty