As Robin Williams was heard to say "Reality: What a Concept!!"
Trump exploits the singularlity of his properties to make wild claims about their value. But if you look at the history of Mar-a-lago the bald fact is that the upkeep is horrendous, and the restrictions on its use, make it very unattractive as an investment.
Most mega wealthy billionaires, don't buy a house, they build one. They don't buy a 100 year old mansion with high maintenance costs, and a historical designation which means they can't change, alter or renovate the property without consent of the local historical society, or change the use of the property.
No one in their right mind with the kind of money needed to buy that place, would touch it with a 10 foot pole. You can't build on it, you can't renovate it, and the maintenance costs are $2.5 million per year. How much would pay for this white elephant?