With ticket sales and pay-TV take-ups sluggish for their bout at the Sydney Entertainment Centre on Wednesday night, the Mosley camp wanted the majority of their $1.2 million upfront.
But when their demands were not met, Sugar turned bitter and headed to the airport with his entourage to board a flight back to Los Angeles.
This was the fight that Mundine hoped would revive his career and possibly lead to a showdown with the famed Floyd Mayweather.
That now lies in tatters.
The Mosley fiasco will scare other potential Mundine opponents from travelling to Australia, while The Man is virtually unknown overseas and can't command a big money fight.
At age 38, his options are extremely limited.
But the biggest loser from the Mosley walkout is Australian boxing legend Jeff Fenech.
He stumped up $500,000 of his own money to secure the fight and is now of out of pocket.
But he has refused to blame the American for running and expressed sympathy for Mundine.
"Something I didn't know in the contract was that Shane had to have money paid prior to the fight," Fenech told Triple M .
"Now someone tells me he's at the airport. I'm not real happy.
"If his contract said he had to be paid that $700,000 prior to him fighting, his management would have just said 'get on the plane'.
"In a way I wished I'd listened to my manager more often and took their orders.
"As upsetting as it is – and I'm going to lose a lot of money – he's got to do what his management says.
"I feel for Shane and I feel for Anthony.
"The big loser is the guy talking to you on the phone because I'm the person who put the money up."