As Michael explained in a telephone interview, the focus on his brother has encouraged the studio to reconsider its obligations to him. “The more often Bill’s name gets mentioned, and the more often he is given public credit for something that he did, the easier it is for me to go to Marvel and say, ‘You might want to consider raising your offer.’ ” …“My attorney is very good,” Michael said. “I’m not going to say Marvel came to me and opened up their hearts and their purse strings.”
On Bill Mantlo getting recognition, credit and renumeration for his work, from here.
Important edit: Mike Mantlo has since said that he was very misquoted by the NYT story – I’ve talked to him for THR for a story that’ll go live hopefully very soon. Suffice to say, he’s pretty much disowned the above quote and is far, far more complimentary about his dealings with Marvel.