One way to stand out with a wedding proposal: via a flash mob. But as this New York Times piece explains, flash mobs are very expensive:

A flash proposal can start at $2,000 for a simple affair, which involves all supporting players — choreographers, videographers, rehearsal rental space and D.J.’s, but Ms. Broussard said that the costs could vary widely because each event is customized. If the would-be groom wants multiple cameras, professional dancers with complex choreography and costumes, the costs can surpass $10,000.

Others who can arrange events include Mob the World in Seattle and dance companies like Hip Hop Craze. For Mr. Jones’s efforts, he hired the choreographer Derek Mitchell, who supplied his own dancers.

On average, about 30 to 50 “mobbers,” often culled from Web sites and related Meetup pages, are brought together for an event. Many of the participants are volunteers who often have no background in professional dancing and receive little to no compensation. Once they register for an event, they are sent a link to the choreographed routine and typically get two days to rehearse.

Mr. Jones, whose engagement event included the band, flash mob and camera equipment, said it cost close to $7,000, not including the expense of flying in relatives. Mr. Centner said the price tag for his Union Square event was $7,300. That figure, too, does not account for some extras.

Some flash mob case studies are in the piece.