Lennox Lewis would consider a return to boxing to face IBF, WBA and WBO champion Wladimir Klitschko for a fee of $100 million.
Lewis, 48, has been offered half that amount to come out of retirement and return to the ring against the Russian.
However, after the proposal was made moot during Klitschko's win over Alexander Povetkin in Moscow on Saturday, the former undisputed heavyweight champion revealed the necessary fee.
"That ($100 million) is my price tag and it is under discussion," Lewis told The Daily Mail.
"I have told them I can be ready in six months and I am in provisional training.
"I said at the time that it will take $50 million to get me out of my pajamas but now I have to consider the value of my legacy of having retired as undisputed champion. That will cost them $100 million."
Lewis' last bout came against Klitschko's brother Vitali in 2003. Lennox won and announced his retirement a year later.
Lewis confirmed his desire to face Wladimir while also lamenting the current state of heavyweight boxing.
"I beat Vitali so I would like to fight the other brother but we'll see how it works out. I want to bring back the Sweet Science to heavyweight boxing," he said.
"In a way this fight (Klitschko vs. Povetkin) confirmed my disappointment with the state of heavyweight boxing right now.
"People paid a lot of money in expectation of a great fight but Povetkin was not properly prepared for the most important fight of his career."