According to rival, Jarrell Miller, Anthony is set to pocket £59million in his rematch against Andy Ruiz in Saudi Arabia on December 7.
The potential purse would see Joshua double his net worth, with Forbes already valuing the heavyweight at £43m.
Miller told FightHub: “Nobody has fought in Saudi Arabia.
“Them fighting in America would have been different. I know the atmosphere would have been different. Andy was hungry [for the first fight].
“Has Andy kind of settled down the last couple of months? Is AJ more hungry now?.
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Miller, 31, was set to face Joshua, 30 before he failed multiple voluntary pre-fight drug tests allowing Ruiz to swoop in and score a 25-1 upset in New York.