A year after the record Damien Hirst sale, works by the artist are again being valued at levels seen at the peak of the art market boom.

Auction estimates -- if not realized prices -- are similar to those seen at Sotheby’s event last September, which raised the most money for a single-artist auction. The “Beautiful Inside My Head Forever” sale made 111.5 million pounds ($199 million). Buyers including Hirst’s dealers White Cube and Gagosian Gallery fought for lots only hours after the collapse of Lehman Brothers Holdings Inc.

An increase in estimates shows some confidence returning to the market after contemporary-art prices dropped as much as 30 to 50 percent this year, said dealers. Wealthy collectors refrained from making purchases in the global financial crisis. Sellers also held back as auction houses stopped guaranteeing prices.

“During the boom, prices were so far removed from estimates,” Anders Petterson, founder of the London-based research company ArtTactic, said in an interview. “The gap between the two has now come together,” said Petterson, who will be publishing a report on the Hirst market in October.

Sotheby’s Oct. 16 sale of contemporary art in London during the week of the Frieze Art Fair includes Hirst’s pale-blue-and- white 2006 butterfly painting “Retribution,” estimated at 450,000 pounds to 650,000 pounds. The 6-foot-8-inch-diameter household-gloss-on-canvas is the same size as, and a similar color to, the 2008 butterfly work “Reincarnated,” which had a low valuation of 500,000 pounds at the company’s “Beautiful” sale last September.