My cousin, who is a very well-paid executive with a major company here in the Pacific Northwest, just completed building her custom-made house on Lake Sammamish about a year ago. It is 7,000 sq. feet (main floor, upper floor, and finished (liveable) basement. Attended her house-warming party last summer. It is a beautiful home and nicely furnished. For her and her family, which includes her husband and 2 young children, I think it is wonderful. I say, if a person can afford it and it suits their lifestyle, go for it!
I can't afford something like that and it wouldn't fit my lifestyle because I'm single, live alone, and don't need or want a lot of space. That's just more cleaning and maintenance for a rather lazy person like me. The house I live in is about 3,000 sq. feet, and I spend most of my time in about 1/3 of the house. I pay a gardener about $60 per month to mow my grass and edge the lawn; I am getting tired of regular maintenance like getting on a ladder and cleaning out the gutters, fertilizing the lawn, weeding, etc. I am not mechanically inclined, so even minor house repairs have to be done by paid professionals or handymen.
I think I would like to live in a square box (with self-cleaning windows and an indestructible roof) about 1,000 sq. feet that consists of a very large kitchen with a sitting/dining area, a bedroom, and bathroom. Parking space for 2 cars. Living room not necessary. No stairs. No lawn. Closest neighbor at least 1/4 mile away.
Maybe a large yurt will do.