Hearn has been targeting a stadium showdown between the two fighters at Wembley.
"We're taking all of the risk - $50 million against 50 percent", DiBella said.
"They are banking on the fight making 20m dollars and Wilder getting 20m against the 12 and a half we offered him".
Joshua's promoter, who is in NY for a Matchroom Boxing USA card in Brooklyn, suggested the offer was a "great PR stunt" but with the two promoters due to meet on Friday, he is now taking it seriously.
"It said to please accept this fight by tomorrow, which makes it feel like a PR move, especially since it has come from Deontay".
"With all due respect to Deontay Wilder, I don't believe he has $50m", Hearn said.
"I've got something special for you", Wilder tells Joshua in the video.
Wilder would then cut to a video of Joshua in a recent interview claiming that "I'll take 50 million up front.
I'm looking forward to our meeting in the ring".
The two fighters are extremely unsafe in the ring. "There are obviously other things that need to be addressed". Al Haymon and I have never not delivered what we've offered. Wilder would like the fight to be in the USA, but his promoter told Sky Sports that is not a deal-breaking point. Joshua has a number of existing broadcast deals in multiple territories [though he is a free agent in the U.S.].
The 28-year-old Joshua (21-0, 20 KOs) won a world title in 2016 and has made five defenses, including unifying three belts with a decision win against Joseph Parker on March 31 in Cardiff, Wales.
Wilder, 32, improved to 40-0 with 39 knockouts when he knocked out previously unbeaten Cuban Luis Ortiz in the 10th round in Brooklyn, New York, on Mar 3.