The 'Scream & Shout' singer, who confirmed her departure from the Fox contest on Friday (January 11), apparently asked for her fee to be increased to $18m (£11m), but bosses decided she "wasn't worth that much".
"After much deliberation, they just felt that Britney wasn't worth that much because she wasn't bringing enough to the table," a source told Perez Hilton.
"Her performance as a judge was scrutinised, and she didn't really add anything to the show. They felt she didn't warrant a $3 million pay hike."
Spears left The X Factor USA after just one season amid rumours that Simon Cowell had been planning to fire her.
The 'Hold It Against Me' star is alleged to have closed a deal for a Las Vegas residency that could earn her up to $100m (£62m) over two years.
Spears also confirmed her split from fiancé Jason Trawick last week.