Does $250 per sf to build house include the cost if gc?

[Bob Ross]

When people talk about the cost per square foot to build a house it is typically 250 or I think 200 in my area (Boston suburbs)

My question is- when people throw around this “generic” number, does this typically include the cost of hiring a gc to build the project? I know gc fees around around 30 percent of the construction cost. So if you would gc it your self would the generic cost be $200-(.3*200)=60

200-60=140. So $140 per sf if you hire your own subs and gc the project yourself?

Also. When throwing out this generic number. I assume this does not include any sf in a finished attic or basement, right?

Thank you