Large houses would only be a waste of money if we know the utility that others get from having a large house. It’s like saying designer clothes, super cars, extravagant hotels are a waste of money, when in reality these items may have more utility than the alternative (ie retiring early). Not everybody wants to retire. I took a break between school and my initial job and was so bored by the monotony that I resolved to never retire unless unable to perform. Even then, I’d still try to teach or do consulting or something