Britney Spears vs. Jennifer Lopez -- It's All About Money

Britney vs. JLoIt's All About the Moolah

Exclusive

Jennifer Lopez helped Britney Spears secure a $15 million paycheck for "X Factor" -- because Britney had one intractable demand ... she had to make more than J Lo did for her first season on "American Idol."

JLo raked in $12 mil for her first season on "American Idol." There are reports she made $20 mil for the season that just ended, but we hear it's less than that.

Sources very familiar with the situation tell TMZ ... Britney's bottom line was no less than $13 mil. But sources connected with "X Factor" tell us Britney initially asked for a lot more -- $20 mil.

As we first reported, Britney and "X Factor" eventually settled on $15 mil for the season.

The wild card now is JLo. It's unclear if "American Idol" will pay her what she's been making because ratings are down and if she can't pull in at least what Britney is getting, ego could make it a no go.

Stay tuned.