I haven't followed the UFC for years since I realized that Dana White was an evil man and the UFC is an exploitative organization which abuses all of its fighters.

But I am guessing that this event will be on Pay-Per-View like most of their events, and so the UFC will cover the construction costs.

But at for who is paying for it, I would argue that all Americans are paying for it as a weakening of the Constitution, as Presidents historically can't favor any specific private company using the White House, which if I remember correctly, are laws related to the emoluments clause of the Constitution.

And all humans everywhere are paying for it as a strike against basic human dignity and the progress of civilization. We're back in Ancient Roman times watching gladiators fight in the Colosseum.