[Obama dances on stage at the Neighborhood Inaugural Ball. Reuters]

Obama's campaign cost a whopping $513,557,218.  Or, $7.39 per vote!

And, after it was all said and done, it was time to party!  With guests and entertainers including Mariah Carey, Sean "Diddy" Combs, Mary J. Blige, Faith Hill, Adam Levine, Stevie Wonder, Denzel Washington, Trudie Styler, Sting, will.i.am, Jamie Foxx, Faith Hill, Shakira, Beyonce, and Alicia Keys came out at the Neighborhood Inaugural Ball to help our new prez show us what moves he has on the dance floor.  He danced til dawn with our first lady Michelle, who was decked out in a beautiful Jason Wu gown.

More photos below: