diddy4Sean “Diddy” Combs spent a whopping $3 million on his champagne-flooded 40th-birthday party at the Plaza for 500 guests. He created a fantasy Garden of Eden-themed room with a $30,000 orchid display, installed his own black dance floor and black chandelier and treated guests — including Jay-Z, Bono, Nelly, Martha Stewart, Christy Turlington, Zac Posen, Kim Kardashian and Denzel Washington — to a silver confetti-drop, courtesy of lighting wizard Bentley Meeker, and a performance by Al Green. Security was tight and even Tyrese Gibson and “Twilight’s” Kellan Lutz had to talk their way into the VIP area. Rapper Fabolous flirted with Rachel Hunter after asking Diddy who the leggy beauty was, while DJ Cassidy was working his charms on Adrienne Bailon. -Page 6