And in airplanes. Airlines like to use those screens in front of each seat as billboards. They're on by default and don't time out, so they keep cycling bright ads while you're trying to sleep. Sure, you can turn yours off, but most of your neighbors won't bother changing the default on state.

Has any American budget airline reached the depths Ryanair goes to make every last cent?

They don't have screens on the seats (too expensive), just a printed advert. But they do play audio adverts on the PA system a couple of times per flight, typically for things you can buy on board.