In an old market hall adjacent to the cavernous center where Art Basel, the gold standard of contemporary art fairs, is taking place, there is a happening unlike anything ever staged here. Called “14 Rooms,” it consists of 14 mini-performances created by artists including Marina Abramovic, Damien Hirst and Yoko Ono, each secreted in a small space behind mirrored doors. Open one door, and there’s a Marina Abramovic look-alike naked and astride a bicycle seat, arms outstretched. In another, identical twins sit in front of identical spot paintings by Mr. Hirst.

“Performance art is usually at the periphery, so why not put it front and center?” said Klaus Biesenbach, director of MoMA PS1 in New York, who organized the project with Hans-Ulrich Obrist, a director of exhibitions at the Serpentine Gallery in London. “It’s a temporary museum. Nothing here is for sale.”

But next door at Art Basel, almost everything is. As big and boisterous as ever, with 285 galleries from 34 countries participating, this fair is still a magnet for the contemporary art world. Spotted at Tuesday’s V.I.P. opening were big-money collectors like Steven A. Cohen, the hedge fund billionaire; Daniel S. Loeb, the activist hedge fund manager and Sotheby’s new board member; Mitchell P. Rales, the Washington industrialist, and his wife, Emily; Jerry I. Speyer, chairman of the Museum of Modern Art; and Daniel Brodsky, chairman of the Metropolitan Museum of Art, and his wife, Estrellita, an independent curator. Few artists ever make an appearance at art fairs but Oscar Murillo, the Colombian-born painter, did.

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A Warhol “fright wig” self-portrait.Credit2014. The Andy Warhol Foundation for the Visuals Arts, Inc., via Artists Rights Society (ARS), New York; Skarstedt

Koons, whose retrospective is opening this month at the Whitney Museum of American Art. Priced at $5 million, it sold on Tuesday to a collector from China, Mr. Zwirner said. His booth also features paintings by the South African-born Marlene Dumas, who has a traveling show opening at the Stedelijk in Amsterdam in September; and canvases by Gerhard Richter, who is the subject of an exhibition at the Beyeler Foundation in Basel.

Mr. Zwirner wasn’t the only dealer touting works with a museum presence. Dominique Levy, a New York dealer, had a 1964 black-and-white comic book drawing by Roy Lichtenstein that was in a show at the Morgan Library & Museum four years ago. It sold for an undisclosed price to an American collector.

“Sotheby’s and Christie’s went through a record cycle, and that gives people confidence,” Mr. Zwirner said. “Basel is our biggest weapon, if we want to go mano a mano with the auction houses.”

Brett Gorvy, chairman of postwar and contemporary art at Christie’s, was here, too. Prices, he said, are “informed by the auctions.” “Collectors have sticker shock, yet they’re pulling the trigger,” he added, using as an example one of Andy Warhol’s “fright wig” self-portraits from 1986 that several people said had belonged to Thea Westreich, the New York collector and dealer. It was bought by another New York collector for around $34 million, according to Per Skarstedt, the dealer who sold it. In addition to examples of Warhol and Bacon — both top sellers at auction last month — Mr. Koons, whose sculptures had adorned the covers of both Sotheby’s and Christie’s contemporary art auction catalogs, was ubiquitous. The Gagosian Gallery is featuring “Hulk (Wheelbarrow),” a giant green painted bronze Hulk carrying a wheelbarrow filled with live flowers; it is priced at $4 million. Almine Rech, another dealer, brought two “Gazing Ball” sculptures made this year, one priced at $2 million and the other at $1.6 million. Both sold to European collectors, she said.

Younger trendy artists are also represented here, with paintings by Jacob Kassay, Joe Bradley and Mark Bradford, many of which were spoken for.

One young artist determined to control his market is Wade Guyton, the American painter who produces canvases on inkjet printers. Last month, protesting an enormous price asked for one of his paintings at auction, he made copies of the 2005 image from the original disk and posted them on Instagram. (Prices for his paintings were stronger than ever anyway, with one bringing nearly $6 million.) Undeterred, for Art Basel he gave each of the five dealers he works with — Frederich Petzel from New York, Gió Marconi in Milan, Galerie Gisela Capitain from Cologne, Galerie Francesca Pia from Zurich and Galerie Chantal Crousel in Paris — a black painting, all the same size and all made from the same disk. They each had a $350,000 price tag, and all of them sold either on Tuesday or before.

In an email, Mr. Guyton explained that he instructed the dealers to hang his paintings at identical heights, “so each time you walk up to one, you would have a similar physical

encounter.” He added: “On the one hand, it is a way to satisfy all my galleries simultaneously and fairly. It’s also a way of talking about the repetitive experience of seeing similar artworks throughout a fair and embracing that aggressively by showing almost identical works.”

For a few years now, people have complained that dealers have been selling or reserving work by sending collectors images of what will be on view in Basel well before the fair opens. That discussion grew louder this week. “Preselling should be forbidden,” said Philippe Ségalot, a private New York dealer whose antics in years past — including hiring a Hollywood makeup artist to disguise him so he could sneak into the fair before everyone and snap up the best works — have become Art Basel legend.

“If I had done that this year,” Mr. Ségalot said, “there would have been nothing to buy.”