$5bn: the cost of saying Donald Trump is a mere millionaire

Donald Trump's response, when an investigative journalist published a book alleging he wasn't the billionaire he claimed, was to fire off a $5bn lawsuit, a typically thunderous gesture from the orange-haired skyscraper mogul and star of the US version of The Apprentice. But when hauled before lawyers to give a testimony in the case and explain how he valued his empire, he gave answers that would have made an accountant blush.

In the 2007 deposition, made public before a court hearing yesterday, Mr Trump said he uses "mental projections" to estimate the worth of his properties, admitted exaggerating the success of his businesses ("who wouldn't?"), and says that his perception of his own personal "brand value" goes up and down with his mood. The upshot is that Mr Trump's actual worth is more mysterious than ever, at a time when he is fighting to salvage numerous property deals from the recession and has seen his Atlantic City casinos business go bankrupt.

Mr Trump says that anyone claiming he is not a billionaire is undermining his business, and that the allegations in TrumpNation, a book by New York Times reporter Timothy O'Brien, had cost him lucrative deals across the world. Mr O'Brien and his publishers were in a New Jersey court yesterday arguing that his lawsuit is ridiculous, and asking a judge to throw out the mogul's claims for $5bn in compensation and damages.

Mr O'Brien wrote that Mr Trump was worth a quarter of a billion at best, and perhaps no more than $150m. At the same time, Mr Trump was telling his banks and Atlantic City casino regulators that his businesses were worth $3.6bn – and telling any reporter who asked that he was worth $6bn.

The difference, he explained, was that his personal "brand value" amounts to around $2bn. "There are those that say the value of the brand is very, very valuable," he said at the deposition, and added: "My net worth fluctuates, and it goes up and down with markets and with attitudes and with feelings, even my own feeling."

With lawyers preparing for yesterday's hearing, Mr Trump remained belligerent over the weekend. Talking to the Wall Street Journal, he promised that Mr O'Brien would "wish he had never heard of that goddam book".

In the deposition, Mr Trump was confronted with evidence that, in public interviews, he had exaggerated his ownership stake in some of the properties that bear his name. There are Trump-branded skyscrapers, casinos, golf clubs and other businesses throughout the world, but many have outside investors or bank loans underpinning them. An assessment by Deutsche Bank, when it underwrote a loan for one property, was that Mr Trump was worth $788m. He said Deutsche did not count all his assets.

There was also a skirmish over the meaning of the word "average". While he publicly claimed that an apartment development was selling for $1,300 per square foot on average, he conceded that "on some units I averaged $1,300" – meaning that this was most likely closer to a best price than to an average.

The developer was asked if he ever exaggerated in statements about his properties. "I think everybody does. Who wouldn't?" he said. "Would you like me to say, 'oh, gee, the building is not doing well, blah, blah, blah, come by the building' – nobody talks that way. Who would ever talk that way?"

At one point, a questioner asks if that means he inflates the value of his properties in general, non-financial public statements? "Not beyond reason," Mr Trump said.