As an art appraiser, I would value the entire exhibit between 450-550 billion dollars. It is easily the most expensive transportable, and technically salable object. However, had it not been restored, because the way the paint was repainted, exposed to chemicals and repainted again, the value would be increase by 300% to anywhere from 1.8 - 2.2 trillion dollars.
Now, it's quite obvious that no one could afford even 1/5th of 550 billion dollars, but I am giving that estimate based on the value if each painting, fresco, bust, tapestry, etc were sold by itself.
I would value the full wall of "The Last Judgment" at about 45-65 billion, so it is better off just to call it priceless because no one person can afford that and no two people are dumb enough to share it.