Why is movie theater popcorn so outrageously expensive?

"When a theater wants to show a film, it must agree to pay the distributor a percentage of all ticket sales. This percentage is higher during the first few weeks of a film and decreases over time, but generally averages out to ~70%.

So, if a theater sells a movie ticket for $9, its cut is only $2.70 — and that’s without accounting for other expenses.

Theater owners could price tickets higher, but it wouldn’t do them much good since 70% of any increase goes straight to the studios. Instead, they think of movies as a loss leader: their primary goal is to get as many people through their doors as possible, even if it means breaking even (or losing money) on the price of admission."