New York (CNN)(CNN) -- An Iranian-Turkish gold trader admitted in a US court that he made "maybe $150 million" by helping Iran dodge international sanctions.
It's a colossal take for a minor Turkish tabloid celebrity who, for years, escaped prosecution in his own country and now faces years in US prison.
Reza Zarrab, once the lead defendant in a widespread money laundering investigation, has pleaded guilty to money laundering and bank fraud among other charges, according to court documents.
He is now the US government's star witness in the New York criminal trial of his alleged counterpart -- a Turkish banker named Mehmet Hakan Atilla who until recently was Zarrab's co-defendant. Atilla has pleaded not guilty.
On Tuesday, his fifth day of testimony, Zarrab estimated how much he made by laundering Iranian money for six years until he was arrested in Miami in 2016.
"I don't remember exactly," Zarrab said. "It could be $100 million. It could be more than that, maybe $150 million."
He said that "after paying commission for the bank and other bribes," he was left with a cut of 0.4%, equal to $4 on every $1,000.
Massive fraud 'wildly possible'
Although Zarrab has not said how much Iranian money he illegally moved through international banks, an 0.4% cut matching his payout would mean that he helped Iran move $25 billion to $37 billion -- an astonishing number for a black-market operation spearheaded by a single man.
That figure has not appeared in court documents. The US Attorney's Office for the Southern District of New York did not immediately provide responses to CNN's questions about the scale of the alleged fraud.
One expert on Iranian sanctions said the $37 billion total was "possible ... maybe more like wildly possible."
"I continue to be surprised how large the profit and level of financial sanctions evasions are. But this would be a stretch ... so I'd be skeptical," said George A. Lopez, a professor at the Kroc Institute for International Peace Studies at the University of Notre Dame.
However, several United Nations reports on the effect of Iranian sanction do indicate that a single person could help Iran launder huge amounts of money. The UN Panel of Experts reports describe how in 2011 "a local businessman" in one country faked documents to transfer $1 billion from Iran's central bank to countries around the world.
During previous testimony in court, Zarrab said that Iran had $3 billion at the Turkish state-owned Halkbank. It was those accounts that Zarrab says he was tasked with emptying to move Iranian funds.
In a written statement, Halkbank denied the accusations: "Our bank did not do any illegal transfers about any country. There is no systematic or conscious violation in order to bypass the embargo."
Money paid for prostitutes
Atilla's defense lawyer, Cathy Fleming, appeared to attack Zarrab's integrity by questioning him on Tuesday and Wednesday about how he spent his riches.
Zarrab admitted that in 2013 he paid for prostitutes to satisfy "others," likely business partners and clients.
He also said he was carrying $102,000 when he was arrested in March 2016 -- cash that the international bank fraudster and money launderer planned to spend on a family trip to Walt Disney World.
"This was the money needed for our 10-day trip for seven individuals," Zarrab said.
He also admitted that, while in a US jail, he used his Turkish lawyer to funnel $45,000 to a US prison guard. It was a bribe so that he could sneak alcohol into the jail and use the guard's cell phone to call family members in Turkey.
Zarrab also admitted paying other jail inmates to use their phone time when his own 300-minute allotment was up.
The closely watched trial took an unexpected turn Wednesday evening, when Zarrab was sued by a former jail inmate who accused him of rape.
The inmate is a man from Ivory Coast who recently pleaded guilty to providing "material support" to a terrorist organization; he had connected the Colombian guerilla group FARC with a weapons dealer.
According to the man's lawsuit, Zarrab raped him, assaulted him with his hands, and sodomized him with a cucumber when they shared a cell earlier this year at Manhattan's Metropolitan Correctional Center.
Zarrab's attorney, Benjamin Brafman, told CNN by email: "Mr Zarrab vehemently denies this outrageous and patently false allegation. He intends to vigorously defend against this offensive lawsuit."
Last week, Zarrab implicated top Turkish government officials when he testified that Turkish President Recep Tayyip Erdogan, who was prime minister at the time, personally intervened in the scheme -- as well as former Turkish economy minister Zafer Caglayan.
Also last week, Erdogan said Turkey "did the right thing" and did not violate US sanctions against Iran, according to CNN Turk. Caglayan denied all allegations in a Turkish probe into these allegations that started in 2013.
The accusations have set off a diplomatic spat between Turkey and the United States. Turkey claims the current American trial is a ruse meant to damage Turkish politicians, and its government has retaliated by moving to seize Zarrab's assets.