The Floyd Mayweather-Manny Pacquiao mega fight generated an eye-watering $US400 million ($A507 million) in US revenues fuelled by more than 4.4 million pay-per-view buys, making it the highest-grossing fight in boxing history.

The welterweight world championship showdown, which Mayweather won by a unanimous decision, may have failed to live up to its hype in the ring, but it did meet the goal of becoming the richest fight in boxing history.

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It nearly doubled the previous record of 2.48 million buys from a 2007 Mayweather-Oscar De La Hoya fight and also crushed the record by more three times for a live boxing gate, American cable networks Home Box Office Inc. and Showtime Networks Inc. said in a joint news release.

It generated more than $US71 million from the sale of 16,219 tickets at the MGM Grand Hotel and Casino for a fight between boxing’s two biggest stars that was five years in the making.

The previous record for a live gate was $US20 million for Mayweather’s 2013 fight at the MGM’s Grand Garden Arena against Mexico’s Canelo Alvarez.

That fight also held the record for US pay-per-view revenue at $US150 million.

Organisers said that by the time they add up all the revenue from overseas pay-per-view buys, close circuit, sponsorship money and merchandise sales that the fight’s gross revenues would top $US500 million.