Sotheby’s auction house called it the “most important collection of contemporary Chinese art to ever come to market” — some 200 works by some of China’s hottest names.And when the first half of the trove, called the Estella Collection, went on the block in April in Hong Kong, it brought in $18 million and set some record prices for artists, like $6 million for a canvas by the Chinese painter Zhang Xiaogang.But the sale of the works has stirred indignation among many of the artists and their dealers and some curators.Those artists and curators say that as the collection was being formed, they were duped into thinking that a rich Westerner was putting together a permanent collection and would eventually donate some of the works to leading museums.Instead, they say, the buyers were a group of investors who quickly cashed in by selling the works last August to the Manhattan dealer William Acquavella, who is in turn selling them through Sotheby’s. (The second half of the collection is to be auctioned this fall in New York.)Some of the artists say they sold works in the Estella Collection at a discount in the belief that the collection would gain long-term renown and help enhance their reputations.“I feel cheated,” said one of the artists, Feng Zhengjie, 40, known for his gaudy portraits of fashionable, lushly made-up women. “I can’t believe it ended up like that, just for an auction.”Michael Goedhuis, the New York dealer who formed the collection for the group of investors, said he never misled anyone and had expected his investors to hold onto the works.“The story was the same to everyone: this is a collection we intend on keeping intact,” said Mr. Goedhuis, who traveled to China for more than three years to collect the pieces. “There was a change of direction for various reasons. It was a big surprise and it was out of my control.”Mr. Goedhuis declined to identify his investors, but The New York Times has already named two: Ray Debbane, president of the New York investment firm Invus Financial Advisors, and Sacha Lainovic, a co-founder and managing partner at Invus. Neither Mr. Debbane nor Mr. Lainovic returned telephone calls seeking comment.Mr. Goedhuis said that in any case the artists had no reason to complain because they had benefited from the exposure. “They’re riding the wave,” he said.In a statement issued last week, Sotheby’s acknowledged that in the final weeks before the sale it “became aware that a few artists had sold their works with a different expectation about what would happen to them in the future.” It said it hoped “the international exposure during this exciting time in the market would be helpful in furthering their careers.”Aggravating the controversy, the auction was announced just after the works had been exhibited at the Louisiana Museum of Modern Art in Humlebaek, Denmark, from March to August of last year. Had they known the Estella Collection would quickly be sold, officials at the Danish museum said, they would never have organized the exhibition.“We seriously regret that it turned out to be mere speculation, and there was dishonesty,” said Anders Kold, the curator of the show, titled “Made in China.” “We didn’t have that information, and so as a consequence, we went on with it.”To retain the public trust and ensure that they are not used as marketing tools, museums generally try to avoid exhibiting private collections that are soon to be sold.The show also traveled to the Israel Museum in Jerusalem, closing there shortly before the April auction in Hong Kong. "At the time that the museum made arrangements for the exhibition, there was no indication of any intention to sell the collection,'' the Israel Museum said this week in an e-mail. "The museum learned of this development only toward the end of the showing.''The conflict suggests the tensions that have arisen between artists, curators, galleries and museums around the world since the booming art market became global. The challenges are particularly acute when it comes to China, which has become a magnet for some of the world’s biggest galleries, museums, collectors and art market speculators, but is relatively new to the game.Chinese artists who a few years ago were selling works for just $10,000 each are suddenly signing deals with international galleries and seeing their works fetch $500,000 or more at auction. Indeed, Art Market Trends 2007 reported that last year, 5 of the 10 best-selling living artists at auction were born in China, led by Mr. Zhang, 50, whose works sold for a total of $56.8 million at auction last year.“It’s amazing,” said Fabien Fryns, a founder of F2 Gallery in Beijing. “I think there’ll be a $20 million painting some time soon.”Mr. Goedhuis, a former antiques dealer, said that last August’s sale to Mr. Acquavella was hugely profitable for his investors. But he declined to say what they paid for the works or what they sold them for. Art market experts have put the Acquavella acquisition at around $25 million.Sotheby’s is a stakeholder in the Estella Collection auction. That the first half of the collection has sold for far above the estimate suggests that Mr. Acquavella and the auction house have invested wisely.Mr. Goedhuis said his investors’ “original concept” was to “build the pre-eminent collection of Chinese contemporary art as the basis of a great book.”One indication of the seriousness of the project, he said, was a decision to hire Britta Erickson, an independent scholar and a leading authority on Chinese contemporary art, to help select works and write essays for the book, “China Onward,” which was published by the Louisiana Museum in Denmark.But Ms. Erickson now says that she too was misled into thinking she was working for a serious, long-term collector.“I believed that it was to be a personal collection being assembled for the long term, with perhaps some pieces to be donated to museums,” she said in an e-mail message. “I am sorry I was misinformed.”She added, “The art world cannot function without trust.”The artist He Sen, 40, who paints photographlike images of young women, also said that Mr. Goedhuis had assured him that a long-term collector was behind the Estella Collection and that some of the works might end up in a museum.He said that one painting that he sold to the collection for about $60,000 went for more than $200,000 at the Hong Kong auction.“Many artists, including me, were convinced by him, gave our best works to Michael, some even at a relatively cheap price,” Mr. He said of Mr. Goedhuis. “Then it turned out to be an auction. We feel sold out by him.”Mr. Feng said his works were auctioned at Sotheby’s for 5 to 10 times the price he gave Mr. Goedhuis.Mr. Goedhuis said that in turning to Mr. Acquavella, he had hoped that the Las Vegas casino tycoon Steve Wynn, a major collector with interests in Macao, one of China’s special administrative regions, would emerge as a buyer of the entire collection. In the end Mr. Acquavella bought it himself, without restrictions. Then he put it up for auction.“That’s what I do,” Mr. Acquavella said. “I buy and sell.”Mr. Goedhuis said he had since tried to convince the artists that the Estella Collection’s brief history was a boon to them.“ ‘You only benefited from this,’ ” he said he told some of the artists after the auction was announced last fall, and he began fielding complaints. “ ‘You’re in a wonderful scholarly book and you’ve been exhibited in two fine museums.’ ”He also offered his own scathing critique of the artists, remarking that they had profited so much from the boom that they could afford to build huge studios and homes.“The problem is everyone is buying and flipping, and the artists are also flipping,” he said by telephone from Beijing. “It’s a Wild West out here.”