Floyd Mayweather's Sept. 12 bout with Andre Berto at the MGM Grand Garden sold roughly 400,000 pay-per-view units, a source told Yahoo Sports. That number, the source said, includes about 145,000 sales from DirecTV, which is almost always the first distributor to report a figure.

Another source close to the promotion of the fight said the figure was higher and estimated it between 500,000 and 550,000.

In any event, the result will be the lowest figure since Mayweather sold 325,000 while fighting Carlos Baldomir on HBO Pay-Per-View in 2006.

Showtime Sports executive vice president and general manager Stephen Espinoza said he did not plan to release the results. Espinoza said his default position is not to release the figures and only does when there are other parties involved who ask that it be released.

He would not speak in specifics but agreed to talk to Yahoo Sports about the difficulty in promoting the last fight of Mayweather's legendary career.

Mayweather was coming off a heavily hyped May 2 bout against Manny Pacquiao that sold a record 4.6 million PPV units and generated a record of more than $400 million in PPV revenue. But there was widespread dissatisfaction with that fight and numerous lawsuits sprung up in the aftermath.

"To a large extent, anything we did coming off of that massive May 2 event was going to feel like a bit of a letdown," Espinoza told Yahoo Sports. "We didn't have available a really compelling list of available opponents. There's been a lot of speculation about a lot of things, but when you got down to it, there wasn't really a long list of available guys and none of them were slam dunk established stories or really compelling storylines."

Leonard Ellerbe, the CEO of Mayweather Promotions, said he had not heard a pay-per-view figure yet. He said no one expected Mayweather-Berto to come close to Mayweather-Pacquiao and said Mayweather has long since been established as the sport's biggest pay-per-view draw.

"At the end of the day, given what we've accomplished, we're essentially competing against ourselves with this," Ellerbe said. "There's no one else at this level, so we're just competing against ourselves."

Cable systems tend to sell a bit more than 50 percent of the total sales of a show. The telephone companies generally account for eight percent or less. The satellite companies, DirecTV and Dish, make up the rest.

Dish has a heavier Hispanic subscriber set so pay-per-view bouts featuring a Hispanic fighter in the main event tend to do better on Dish than ones without. Espinoza told Yahoo Sports that the undercard featured several Hispanic fighters for that reason.

He said that despite the comparatively poor results of the Mayweather-Berto fight, Showtime was very pleased with its six-fight deal with Mayweather. He said he'd "do it again in a heartbeat."

The live gate hasn't officially been announced, but Ellerbe told Yahoo Sports on Wednesday that it would be at least $10 million. The announced attendance on Saturday was 13,359, about 1,000 shy of a sell-out. Mayweather has the three largest gates in Nevada history and five of the top six, led by $72 million for the Pacquiao fight.

His May 4, 2013, bout with Robert Guerrero had a live paid gate of $9.9 million.

Mayweather was guaranteed $32 million. Berto was guaranteed $4 million, though Showtime did not guarantee all of that money.

Even if the fight sold on the upper end of what the promotion source estimated at 550,000, that would generate about $20.6 million for the promotion. At 550,000 sales, that would do $41.2 million in gross PPV sales. Half of that goes to the television distributors and half to the promotion.

Assuming Ellerbe is correct about a live gate of $10 million, that would account for $31 million going to the promotion. There are, however, other sources of revenues, but that shows that the fight wasn't nearly as successful financially as any of the first five Mayweather bouts on the Showtime contract.

The Mayweather bouts with Pacquiao and Alvarez combined to sell nearly 7 million on PPV. The two bouts with Marcos Maidana and the bout with Guerrero combined for about another 2.7 million. The Berto fight should be enough to push the total pay-per-view sales during Showtime's contract with Mayweather over 10 million.