I doubt that people in the market for a downtown apartment share the same priorities for selecting a home as people who would buy a McMansion. I also don’t think you can equate 10,000 sq ft over multiple floors with the same area on a single floor. I don’t know how that space would be designed in any practical manner that wouldn’t turn it into a labyrinth. I guess if someone wants a ballroom or a basketball court in their apartment?
Rural areas are replete with relatively average 2k sq ft houses with 10k sq ft+ “workshops” or “barns” - which often are just big areas that never actually did any farming, but are used for storing toys or hobbies.
