Many high end houses can take years to sell.
“Donald Trump reportedly paid $10 million for his Mar-a-Lago property. This is significantly less than his original offer of $25 million. The sale included 17 acres of land and all the original home furnishings. He also later purchased the beachfront property in front of the estate.”
https://www.cheatsheet.com/entertainment/donald-trump-mar-a-lago.html/
Especially if the location is meh, as Michael Jordan found out the hard way.
People with that kind of money will pay for the location, not the house itself. They will just tear down the house and build the one they want.
My Dad bought his home in 1964 for $12,000.
Zillow lists it for $930,000 today.