If it is true about the military bunker capabilities due to the steel and concrete construction then knowing the future "Trump Branding" would increase it's valuation exponentially as part of our society, let alone our history due his Presidency; we are left with a value proposition equal too or beyond that of Buckingham Palace.
We haven't even gotten into the valuation of what Melania's countenance has brought to the property, for all those believers in angels, that would be priceless.