Except because he got that tax break, it can't be developed. He got it zones as "Large residential". This is why the tax appraiser valued it at between 18 and 27 million.
It’s a unique property that experts say would fetch hundreds of millions of dollars. But a billion? Here’s why it matters.
www.tampabay.com
Siding with New York’s attorney general in a lawsuit accusing Trump of grossly overvaluing his assets, Judge Arthur Engoron found that Trump consistently exaggerated Mar-a-Lago’s worth. He noted that one Trump estimate of the club’s value was 2,300% times the Palm Beach County tax appraiser’s valuations, which ranged from $18 million to $37 million.
It also has significance as a historical site, which also limits what can be done with it. (Not that hasn't stopped Trump from making it into a gaudy Persian Palace). Trump has also pulled cute stunts like burying his dead ex-wife there to give it a tax break for being a cemetery. This would further limit what a future buyer can do with the property. We've all seen Poltergeist!
Again, everyone does it is not a legal defense. That Trump got away with something for a long time, doesn't mean he wasn't breaking the law.