He also told me he was ready to sue the comedian Bill Maher, who claimed on The Tonight Show in January that Trump was the product of the union of a human mother and an orangutan father. Maher offered $5 million to Trump for proof that this was not true. Trump then sent Maher a copy of his birth certificate, apparently without irony. But he had not heard from Maher or received the reward, which he said he would split among five charities. “He has not responded, and the reason he hasn’t responded is his lawyers probably tell him, ‘You’ve got yourself a problem,’ ” Trump explained. “But if he doesn’t pay, I will bring a lawsuit.” (He made good on his word, filing a suit against Maher on February 4, demanding the $5 million. Maher later said, on his show, “Donald Trump must learn two things—what a joke is, and what a contract is.”)

These legal musings aside, the question hangs in the air, like a trailing wisp of cigar smoke: Why did Trump spend five years—and by some estimates millions in legal fees—to pursue a libel suit against O’Brien when he had to know, as a larger-than-life public figure, that the bar he’d have to clear to win the lawsuit would be incredibly high? Why is Trump’s net worth so important to him that he has to hit people over the head with it?

“I think it’s very important to him, psychologically and emotionally, to be considered fabulously wealthy, because I think he sees it as part of a pecking order and a symbol of his arrival,” O’Brien told me.

Trump said the reason was far simpler. “I like people telling the truth,” he explained. “When people don’t tell the truth, I go after them, and I don’t like that. For instance, there have been many bad things said about me over the years, and in some cases they’ve been true. It doesn’t bother me. If I have a fault and somebody exposes that fault or talks about that fault, you won’t hear me complain. If I make a mistake and somebody brings it up, you won’t hear me complain. But when people make things up, or when people do things knowingly wrong, I always bring it up, even if it’s not so bad.”

He also seems to enjoy wasting the time and money of those without his deep pockets. “I’ll do what I have to do,” he continued. “Even if I’m not going to win. I do it because at least you can inflict pain that way on somebody, in terms of legal fees and other things.” A moment later, he added, “So now my net worth is over $8 billion, substantially over $8 billion, with a lot of cash, and everybody knows it.”

He said he doesn’t understand why this “ancient history”—the O’Brien libel suit—is worthy of additional ink. He told me that when he first filed the lawsuit, one of his friends called him and told him that just by filing, he’d already proved he was really rich, because he was willing to show in court just how rich he was. “And I proved that I was much richer than anyone knew, but unfortunately, the judge basically said I wasn’t damaged,” he explained. “In other words, they said his story didn’t damage me, didn’t have any impact. The judge said I wasn’t damaged. But if you could, William, I don’t think you should even bring that up.”

The perception of Trump’s enormous wealth is essential to everything Trump, whether his fortune is the $8 billion he now claims or the $3.1 billion that Forbes estimated in September 2012 or something else altogether. It’s why he jets off to Mar-a-Lago on the weekends in his new Citation X—“What I like about that is the speed,” he explained. “It’s the fastest private plane ever made. It goes Mach 9.3”—and why he is letting the Discovery Channel feature his Boeing 757 business jet on an upcoming show. (A three-minute YouTube video hosted by Amanda Miller, a Trump associate, lovingly shows off the jet’s dining area, the flatscreen TVs—complete with a button that immediately accesses Trump’s favorite films—and, of course, the bedroom. It’s Cribs for billionaires.)