Even billionaires go to bashes at other moguls’ pads to see how the other half of the 1 percent lives.

At a recent party at Blue Dream — the East Hampton home of real estate magnate Robert “Bobby” Taubman and his new wife, Dallas broker Caroline Summers — a spy told Page Six, “The party was the talk of the town on Labor Day. Everyone, including all the billionaires, wanted to see the house — and everyone invited came to the party.”

The source said, “Mouths and jaws dropped at Blue Dream, the house is a work of art.”

The home, by the architects behind Manhattan’s High Line, Diller Scofidio + Renfro, is the subject of a new DelMonico Books tome that came out last week, “Blue Dream and the Legacy of Modernism in the Hamptons.”

The modernist marvel was just profiled in the Wall Street Journal’s Mansion section.

We hear the event was in celebration of Taubman and Summers’ May wedding, and that guests included society architect Peter Marino, former New Jersey Gov. Jon Corzine, former Sears CEO Eddie Lampert, John and Susan Hess, billionaire developer Steven Roth and his producer wife, Daryl, Patriots owner Robert Kraft and Dr. Dana Blumberg, Chicago tycoon Neil and Kimberly Bluhm, and former Barney’s chairman Richard Perry and his designer wife, Lisa, among others.

Spies said the party cost a cool $1 million.

“There was a tent in the garden with a singer and a classic big band,” said a source. “Champagne flowed and huge tins of beluga caviar were everywhere. A fun after-party was held in the house.” And, “because of the high-profile guests, there was lots of security.”

Blue Dream was the brainchild of Taubman’s beloved late art collector wife, Julia, and named after a strain of weed favored by her author pal, Elmore Leonard.

Summers did not respond to a request for comment from Page Six.

Taubman’s father was mall magnate and art collector, A. Alfred Taubman, who famously bought Sotheby’s in the ’80s and took the biz public, and was also caught up in a subsequent auction world scandal.