"The show would suffer significantly if they were not there," he said. "If you take Simon Cowell off 'American Idol' is it still 'American Idol?' No, I think it becomes a run-of-the-mill talent show."
Belloni said Cowell has been vocal in the past about his willingness to leave the show. The acerbic British judge has his hand in a lot of pots, including co-producing and co-judging "X-Factor," a U.K. musical talent show. Belloni said, in the past, Cowell has tried to make bringing the "X-Factor" to America part of his deal with "Idol." Fox refused but could do so this year to hold on to Cowell, Belloni believes.
"American Idol" producers declined to comment to ABCNews.com about the contract negotiations, and Cowell's rep did not respond to a request for comment.
Compared to Cowell, fellow judge Paula Abdul is making pennies. Though Abdul is looking for a significant raise from the $4 million to $8 million a year she reportedly makes, Fox appears to be playing hardball.
Her manager David Sonenberg did not respond to an ABCNews.com request for comment, but last week he was vocal to the Los Angeles Times about the show's "rude and disrespectful" treatment of Abdul.
"Very sadly, it does not appear that she's going to be back on 'Idol,'" Sonenberg told the Times.
"I find it under these circumstances particularly unusual; I think unnecessarily hurtful," he added. "I find it kind of unconscionable and certainly rude and disrespectful that they haven't stepped up and said what they want to do."
Quoting sources close to the show, the Times said Monday that Abdul was asking for as much as $20 million but had come down to $12 million.
After Cowell, Santilli believes Abdul is the most valuable person on the show. "I don't agree with people who say she is too flaky," she said. "She is sort of the heart of the panel, she's on the kids' side."
"I think the show would suffer without Paula," Santilli said. "It would recover, but it wouldn't quite be the same."
But Santilli believes if Abdul sticks to her demands, Fox may just let her walk.
"I think in my heart she's going to come back," she said. "I really hope she's not that stupid."
One person who is dispensable, Santilli said, is new judge Kara DioGuardi.
"If Kara left next year, it would probably be fine. She never did quite gel with the rest of them," Santilli said.
Belloni said he's unsure about DioGuardi's return. "I would think if she were coming back we would know by now," he said.
If Fox learned anything from last season's DioGuardi experiment, it's that "Idol" fans like the combination of Seacrest, Cowell, Abdul and co-judge Randy Jackson.
"That's the equivalent of a cast," he said. "You could take somebody out of that mix but it's a risk. Do you mess with the No. 1 show on television at a time when it has vulnerabilities?"
Belloni is referring to the "Idol's" ratings, which fell in recent seasons. The show also took in less advertising revenue last season than the one before.
And just like in the scripted world, by the time a reality show has peaked, producers find themselves paying more to the talent.
"If you want to keep a show on the air you have to pay the talent," Belloni said. "It stays on the air because it's a brand and people know it. But it becomes so expensive that the network has to decide if it's worth it."
For now, "Idol" is still worth it.