cddt: I would imagine that someone with a $5m+ house isn't anywhere near close to being underwater.
In house financing, being "underwater" means the homeowner owes more on their mortgage than the home is currently worth.
High-end properties often experience sharper price swings because their value is more speculative, not just supply and demand.
The more it costs, the fewer people can afford it. Also expensive properties take longer to sell in downturns, increasing the risk of being stuck with an underwater asset.
Some admittedly stupid luxury buyers finance large portions of their homes, assuming continued appreciation.
For houses that are heavily over-designed, it may make it hard to sell. While it's may be a dream for someone to have a luxury kitchens in Italian pink marble, extensive landscaping, water features, gym and theatre, it may make the house harder to sell.
I know I saw this property that was a converted hospital. It had a giant plot, with unbelievable amounts of landscaping, and lots of outbuildings. They must have had someone who worked 40 hours/week maintaining the garden. I can imagine they were having a lot of trouble selling it.


