Tyson Fury has been retired for seven weeks and admits nothing has changed since calling time from the sport.
Fury retained his WBC heavyweight title by defeating Dillian Whyte inside six rounds in April at Wembley Stadium.
"Even that £200million report today, that didn't even tempt me," said Fury.
"That would be like half of what I would want to come out of retirement. I'd probably want half a billi to come out of retirement.
"I'm telling you the truth, if you want me out of retirement it's gonna cost half a billi."
When asked about a fight against Joshua, Fury added: "He ain't a virgin anymore, he's been battered from pillar to post by a fat man on three weeks' notice and by a middleweight.
"Usyk hasn't [been beaten], but that's a middleweight coming up from cruiserweight to heavyweight, none of my interest at all.
"If it's half a billi, then I won't say no, will I?
"What you've gotta do is go and get half a billi, and then the Gypsy King will come out and solve all his problems for him," Fury said about a possible comeback.
"Because if AJ gets beat again off Usyk, then there's only gonna be one man to redeem this great fighting nation of the United Kingdom and he goes by the name of Tyson Fury.
"I can solve all the problems, the embarrassment, all that stuff that's gonna happen.
"One call, but it's gonna cost half a bill. 500 million pounds or dollars, I don't care, as long as it's half a billi."
Fury could not resist a dig at Joshua when asked if he was scared or intimidated at the prospect of facing him.
"Oh, I'm terrified of him.
"He's got a chin of granite, heart of gold, he's got everything that a fighting man should have.
"Oh, I'm absolutely shaking in my boots."