A bidding war for the film ratcheted the price up to $10 million, Daily Variety reported Sunday.
The film debuted in Park City, Utah Friday night to a standing ovation, The Reporter noted.
Focus Features, the Weinstein Co., Miramax Films, Warner Independent Pictures and Paramount Classics immediately launched bids.
"This is what Sundance is all about," Searchlight's Peter Rice told The Reporter. "To find this perfect gem of a movie that can be experienced with an enraptured audience. We look forward to sharing it with the world."
The film will be released by Searchlight in the summer, he said.