Christina Aguilera was just one of the performers at what may be the most extravagant and expensive L.A. wedding of the year.

Kurt Rappaport, who has found and sold homes for a slew of the biggest celebs in town got hitched to Sarah Mutch at his Malibu mansion.

Sources involved in the wedding tell us it costs north of a million bucks to pull off, and the people we've spoken with say it was spectacular.

Among the guests ... Diddy, Ryan Seacrest, DJ Khaled and Larry King.  Those two on the right in the pic are Kurt and Sarah.

THE WEDDING DJ

DJ Ruckus was the DJ for the night.

Check out Kurt's house.  BTW ... best cement pond in L.A.