According to US Weekly

Party planners have a list of "who charges what" to perform or appears at your fabulous event.
It goes something like this:
* Mariah Carey private performance - $1,000,000
* Usher private performance - $1,000,000
* Dr. Phil speech - $750,000 - $1,000,000
* Nicole Kidman party apperance - $500,000 + jet
* Jessica Simpson private performance - $400,000
* Scarlett Johansson party apperance - $200,000
* Demi Moore party apperance - $200,000
* Nick Lachey party apperance - $100,000
* Pam Anderson party apperance - $75,000 - $250,000
* Adrian Grenier private performance with band - $35,000
* Tara Reid party apperance - $10,000 - $50,000