Tax assessment not being the value assessment is irrelevant. The properties aren't worth anywhere near the amounts Trump claimed. His Trump Tower apartment is 10,0000 square feet, not 30,000 square feet, and Mar-a-lago is not and has never been worth a billion dollars.
Trump encumbered Mar-a-lago with so many building restrictions that the land cannot be used for anything other than a golf course and beach club, which seriously reduces the value of the land the club sits on. It also has a persistent bed bug problem.
Now that Trump is no longer President, the property is worth 3 times income, which is approximately $25 million per year. $75 million is still 10 times more than he paid for it. Which is about right, if he had kept it in better condition.