Land, driveway, number and quality of fixtures, electrical hookups, cabinets, countertops, doors, clearing land, water, sewage, etc can be nearly identical costs for a 1,000 sf or a 3,000sf home. Many things like wall insulation and heating demand increase sub linearly with square footage.

Which is why home builders so heavily favor large homes by historic standards. This is slightly less true of high rises, but making the building wider doesn’t require more elevators, internal hallways, etc.