Tucked away in a corner of Floyd Mayweather’s changing room at the MGM Grand in Las Vegas is a space reserved for a black Nike duffel bag that remains with him at all times.

Safeguarded by a member of the 38-year-old boxer’s extensive entourage, and weighing in at around a stone, it’s used to transport the ‘bricks’ of cash that he likes to plough through during the course of a typical day.

Staff call it the ‘pregnant duffel’, for a simple reason: it’s always bulging with money.

Last night, in advance of Mayweather’s long-awaited showdown with Manny Pacquiao, that bag’s contents included five shrink-wrapped bundles of $100 bills, each bundle worth some $50,000.

This not-so-petty cash had been set aside to finance the first couple of hours of what the famously brash fighter, who is undefeated in 47 professional bouts, confidently expected to be a raucous victory celebration.

Festivities commenced shortly after last night’s fight finished, at one of Sin City’s many strip clubs.

Mayweather, wearing one of his collection of gold and diamond watches, and dripping with jewellery, arrived in one of the hundred supercars he had purchased from a single dealership since moving to Las Vegas 18 years ago. (Only last week, he boasted of having just spent $450,000 on a bespoke Mercedes, and a six-figure sum on a gold-plated golf buggy as a birthday present for one of his infant sons).

Once inside the strip club, where he was joined by such friends as singers Justin Bieber (who carried his championship belt into the ring before the fight) and Beyonce’s husband Jay-Z. Undoubtedly, Mayweather performed another favourite trick: throwing bundles of banknotes into the air above the venue’s stage, in order to ‘make it rain’.

The atmosphere, an insider was quoted saying, was ‘wall-to-wall money and strippers’. Local lap-dancers were expecting their biggest payday since 2008, when Mayweather and a hip-hop artist called T.I. flew hundreds of their peers to town for a ‘strip off’ competition, with a $100,000 first prize.

So it goes in the strange, vulgar world of an athlete who — thanks to stratospheric talent, and a knack for self-promotion — has succeeded in becoming the world’s highest-earning sportsman, according to Forbes magazine, with an estimated $400 million fortune and earnings that last year topped $105 million.

With the victory of last night, Mayweather, in roughly 45 minutes of action, added around $200 million to that pot, taking 60 per cent of the $300 million purse. His opponent Pacquiao, who was also born into abject poverty, and has lost just five of his 64 professional fights, banked the remainder.

The gargantuan purse makes this the single most lucrative fight in history (little wonder that Mayweather revels in the nickname ‘money’). And its commercial appeal lies squarely in the way that both men have, in very different ways, achieved a sort of celebrity that transcends sport.

Mayweather’s take on fame is perhaps best summed up in a self-portrait he uploaded to his Twitter feed in early January.

Shot on an airport runway, it showed the boxer standing casually on the tarmac, next to his private jet and no fewer than seven of his supercars, worth a cool $15 million. ‘Welcome to my world,’ read the caption.