The hottest opera ticket in New York right now is an absurdist post-rock pageant about clothes. And golf-playing ducks. All four performances of “What to Wear,” the collaboration between the composer Michael Gordon and the experimental theater director Richard Foreman [co-produced by BMP and Bang on a Can] at the Brooklyn Academy of Music’s Harvey Theater, are sold out. On resale sites, you can still snag a ticket for $700 — much more than the cost of parterre box seats at the Met.