The Parry Mansion in Indianapolis was for sale a few years ago...if I recall correctly, for under 600K. This house is over 20,000sq ft. There's a 50'x100' marble floor ballroom, etc. Just completely over the top. well, the investor who bought it just is finishing the restoration on it. Price will be in the multi-millions:
https://www.eventbrite.com/e/parry-mansion-tour-tickets-11198443847