LOS ANGELES — Floyd Mayweather Jr. reached into a backpack and held out a $100 million check for the crowd of 11,000 fight fans to see.

“Let me show you what a $100 million fighter looks like,” he said.

Conor McGregor interrupted from his stool behind the podium: “That’s to the tax man.”

Mayweather replied: “You’re right. I’m the IRS, and I’m going to tax your ass.”

The undefeated boxer and the Irish UFC champion have thrown their first jabs in a summer of verbal sparring before the fighting spectacle of the year.

Mayweather and McGregor kicked off a four-city promotional tour Tuesday at Staples Center, facing off in front of a raucous crowd that thoroughly enjoyed this circus’ first stop in Hollywood. Both fighters promised a knockout, and they had a prolonged shouting match during their second faceoff, with UFC President Dana White stepping between them.

“I am fighting, and he is boxing,” McGregor said. “It’s two men at the top of their game competing. It’s two worlds colliding. That enough is reason why this is what it is.”

All but the most naive fight fans realize the promotion for this bout could be much more entertaining than the historic 154-pound fight Aug. 26 in Las Vegas.

McGregor and Mayweather traded clever insults and profane boasts that quickly showed why this boxing match should be a rare spectacle – before the opening bell, anyway.

“He looks good for a seven- or eight-figure fighter, but I’m a nine-figure fighter,” Mayweather said. “This (guy) made 3 million dollars his last fight, but we know that’s training camp money for me.”

The 40-year-old Mayweather has been coaxed out of his latest retirement for the colossal payday coming from this unique matchup. The bout will cost $99.95 on high-definition pay-per-view, while tickets at T-Mobile Arena will range from $500 to $10,000 – and there aren’t many $500 seats.

In a tailor-made pinstripe suit that repeated a profane phrase in tiny letters as its stripe, McGregor didn’t try to disguise his glee at the prospect of his mammoth financial reward for seeing how his heavy hands can fare against Mayweather’s famed defensive skills in this cross-disciplinary experiment.