A federal judge in New York threatened to reject a $537-million settlement of lawsuits brought by customers of Sotheby's and Christie's auction houses in a price-fixing case, just weeks after tentatively approving it. U.S. District Judge Lewis Kaplan said lawyers who reached the deal tried to satisfy his concerns by tinkering with the numbers rather than adequately modifying the settlement. He gave them until Monday to let customers of the auction houses who believe they were cheated in foreign auctions sue in the United States, something the tentative deal had disallowed. Otherwise, he said, the deal will be tossed out and a trial date set. He noted that the lawyers, led by David Boies, had earned fees of $26.75 million that could be paid once the settlement became effective. Boies is the lawyer who argued the government's antitrust case against Microsoft Corp. The lawyers "gained a powerful incentive to protect the settlement and thus their large fee," Kaplan said.