Katy Perry's $25 million deal to join 'American Idol' has reportedly caused major drama at the ABC network

A source explained: "ABC was originally going to spend no more than

$50 million on talent. They had to expand their budget for Lionel."

Katy's staggering salary was personally signed off by ABC President Ben Sherwood.

But it's been claimed that Katy's fortune has come at the expense of the other judges, both of whom are being paid considerably less to appear on the show.

The insider told the New York Post newspaper's Page Six column: "Ben Sherwood blew the budget on Katy without thinking how that would impact other areas of the show budget. He gambled on her because of her appeal to a younger audience and huge social-media following.

"But Katy is effectively taking money from the other judges, who then had to be paid way less."

In the end, though, the ABC network has been forced to increase its budget for the show in order to secure the services of Lionel and Luke.

The source explained: "The negotiations with Luke and Lionel have been fraught and difficult because of [Katy's deal].

"They expected similar deals to Katy, but are, in fact, getting a hell of a lot less. In the end, ABC had to cough up a second round of money to sign the other judges."

The duo were both initially offered deals worth around $2.5 million each, but Luke and Lionel ultimately reached an agreement for around

$7 million each.

The network insider added: "If 'Idol' doesn't work, it will blow up big time in Sherwood's face. If it does work, he's a genius."