For most big boxing matches in Las Vegas, it isn't very hard for a celebrity of any magnitude to come away with a free ticket to the fight. For the May 2 mega clash between Floyd Mayweather and Manny Pacquiao at the MGM Grand in Las Vegas, that's another story.

Even A-list celebrities like Rihanna will have to fork out the big money for a ticket -- unless they are willing to be a human billboard, according to TMZ Sports.

VOCO Vodka and Coconut Water are two companies who have shopped the offer to at least Rihanna, Leonardo DiCaprio, and Will Smith, TMZ was told.

This comes out after we've already learned that even gamblers are having a hard time locking up seats to the fight. Pacquiao's promoter Bob Arum said that the MGM Grand is requiring at least a $250K line of credit with them just to be considered for a comped seat.

It's also a unique situation for other reasons than being the most anticipated boxing match in decades. For starters, it is a joint venture between premium cable rivals HBO (who has a deal with Pacquiao) and Showtime (who has an insane guaranteed deal with Mayweather). Usually, the networks are allotted a certain amount of comped tickets to hand out -- but with two networks handling the fight, the number of tickets becomes scarce.

Fans should also expect to fork out an all-time high amount just to watch the bout on pay-per-view. It is expected to destroy the previous PPV buy-rate record for a fight set by Mayweather's September 2013 clash against then-unbeaten Mexican star Canelo Alvarez, which did 2.2 million buys for nearly $150 million.

Pacquiao is a betting underdog for the first time since he went up two divisions to conquer Oscar De La Hoya in December 2008. Money has come pouring in on Pacquiao, however.

Check out Manny Pacquiao discussing the fight on CNN from a few days ago in the video below:

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