Let’s see this more reasonably. Contrary to the popular belief, movie theaters don’t make as much money really. Whatever they get in tickets and foods, a large portion of that goes in paying rents, taxes, salary, electricity, and to the production house. The remaining amount isn’t too much.
Coming to your question, why PVR (and other multiplexes) charge too high for popcorn's and other food items is because that is how they make money and affords everything. Besides, so many people are ready to pay the asked amount, so why would they shy away from that?! They would charge high! So stop believing that these brands are looting you. They are just trying to meet their ends.
(Note: I am not saying that they are broke and earn very less. But the assumption that they are making lakhs and crores in profit every month is absurd)
Now, you would ask why government doesn’t take any action against such high price—it is because the price of food and beverages there set by the multiplexes themselves at their convenience and budget. Why does that happen? See, when you buy something in package or can, you pay according to the MRP. However, there is no regulation to the price of foods that are unpacked. And when you buy food in PVR, INOX and more, the foods there are usually unpacked. So they are not guarded by the MRP.
And since the price doesn’t come in the exist regulation and policies, the government can’t really take any definite action.
I'm no expert in this but I have wondered the same and after once again paying for dull and flat popcorn yet again and complaining to the theatre with them replacing the pack with an equally flat popcorn, I went home and read a bit about it. From some of the news and analysis articles discussing revenue streams of movie theatres I have read, apparently movie theatres don't make as much money on the movie tickets as after paying for the movie rights, upkeep of the theatre, services, pay, insurance and taxes they don't make much. So they compensate by selling us exorbitantly priced popcorn and food and drinks ! i was so surprised but with my inexplicable craving for popcorn the minute I am in a movie theater multiplied by the number of people in the queues apparently addicted to movie popcorn like myself, no wonder it's a big revenue stream.