By Edward Chaykovsky

Leonard Ellerbe, CEO of Mayweather Promotions, says WBC/WBA welterweight champion Floyd Mayweather Jr. (48-0, 26KOs) is going to retire after his September 12th title defense against Andre Berto at the MGM Grand in Las Vegas.

Ellerbe denies that Mayweather is fabricating the angle of "final fight" to enhance his per-per-view purchases against a very significant underdog. Some betting circles have Berto as high as a 80-1 underdog.

The Showtime Pay-Per-View will have a rate of $64.95 for standard and $74.95 for high definition.

"That's a fact. This is Floyd's last fight," Ellerbe said to Mlive.com. "I'm not trying to sell it that way. This is going to be his last fight. And the fans get a chance to see Floyd in a very, very exciting fight with a guy that we know is coming to fight."

A victory over Berto would bring Mayweather to 49-0 - matching the unbeaten record of legendary heavyweight great Rocky Marciano.

Many industry insiders expect Mayweather to return next May, with the prospect of going 50-0 being a very high selling point for a pay-per-view event against the right opponent.