“The movie opened on 7,000 screens, including Imax screens, of which only 2,100 were equipped with 3-D technology. About 56 percent of the movie’s weekend total came from those limited 3-D screenings, according to Paramount, and they carried premium prices of up to $4 atop the standard admission. So about 30 percent of the screens delivered 56 percent of the gross, indicating that audiences sought out the format.” (via 3-D Helps Propel Success of No. 1 Film ‘Monsters vs. Aliens’ - NYTimes.com)
Source: The New York Times