Then open up the brand new one -- I would style it "Mad Mayor Bloomberg's Courthouse" -- for viewing in the public areas for $5 for the day or something. Could put in a restaurant and souvenir area, etc. More money could get you a guided tour through the non-pubic areas. We could advertise it on other continents as a tourist attraction. Sure, we are not talking of the Statue of Liberty -- but it would be sort of a government waste wonder of the world. Tours through the entire building could take half a day -- empty area, after empty area, after completely wasted empty area.
Even if we did not pick up that many millions in tourist money ($400 millions is a lot to make up!), the exhibition could save the city millions every year by inspiration not to repeat the mistake over and over in smaller ways -- could potentially save the country billions a year by the same example.
Could not do it with the $670 million dollar new courthouse in Brooklyn -- which I assume is an equal story of waste; but I'm from the Bronx. Same opening after crime went down 75% but it doesn't look like the first building site erected by Martians when they landed -- all glass and flying saucer jury selection space to boot. As a matter of fact the Brooklyn boondoggle looks like an very expanded version of the older, landmark courthouse up on the Grand Concourse -- so it seems the landmark could not be too outmoded.
Just an idea.