Floyd Mayweather is taking a whopping pay cut for his fight with Andre Berto

FLOYD Mayweather is 'Money' for a reason.

The highest eaing athlete on the planet is set to take a staggering 87.2% pay cut for his 49th and final fight with Andre Berto on Sunday in Las Vegas.

Mayweather famously eaed $350 million ($US250 million) for his unanimous points decision win over Manny Pacquiao in May, but his next fight will barely scratch the surface of the so-called 'fight of the century' purse.

The 38-year-old undefeated fighter is set to ea a minimum $45 million for his farewell fight, according to the Nevada Athletic Commission.

That's a pay cut of $305 million.

Berto will ea a minimum of $4 million.

Forbes announced in June, Mayweather was the highest eaing celebrity of the 2015 financial year with eaings estimated at more than $300 million.

ESPN reports similar numbers, but claims Mayweather is set to finish 2015 with eaings of $398 million - for just two fights.

This was a fair pay day for Floyd Mayweather and Manny Pacquiao. Source: Getty Images

His famous rumble with Pacquiao grossed more than $600 million, including a record $73 million in ticket sales.

His welterweight title defence against Berto at the MGM Grand Garden Arena is the final fight of the American's six-fight contract with Showtime/CBS.

Mayweather reportedly eaed $45 million for his 2013 fight with Robert Guerrero, $59 million for his fight with Canelo Alvarez and $45 million for both of his fights with Marcos Maidana.

Mayweather's push to equal heavyweight legend Rocky Marciano's record of 49 unbeaten fights hasn't captured the publicity of his fight with Pacquiao.

Berto is rated a heavy outside, having lost three of his past six fights.

The fight has also been overshadowed by accusations he violated anti-doping rules.

The unbeaten pound-for-pound king was forced onto the backfoot today after it emerged that he had received an injection of vitamins and minerals on the eve of his superfight with Manny Pacquiao in May, breaking World Anti-Doping Agency (WADA) regulations.

Money Mayweather will ea a few more dollars than Andre Berto. Source: AFP

The United States Anti-Doping Agency (USADA) leapt to Mayweather's defence and the man himself said he was 'very proud to be a clean athlete.'

Mayweather says that he wants to write his name in the history books before he hangs up his gloves - not that many believe he will really retire and there have been growing rumours of a rematch against Pacquiao.

Mayweather's critics - and there are plenty of them - accuse the American of bigging-up the quit talk to drum up interest in a fight against Berto that has threatened to become a box-office flop: there are still hundreds of tickets available.

'You have fighters that may be faster than me, there are fighters that may hit harder than me, you have fighters who are very athletic, but you don't have a fighter who can make adjustments like me,' Mayweather told the final pre-fight press conference.

'It's never personal for me, it's always business. Everyone fights for what they fight for. My thing is this: I keep my eyes on the prize. I don't focus on things outside the ring. I focus on the guy in front of me.'

He added: 'I want my legacy to be of a remarkable fighter inside the ring and a great businessman outside of it.'