I know this is an old thread but I saw this video and thought of this thread.
When I was in high school, I used to have a very small income and spending a bunch of popcorn and a drink was a big deal so I came in chewing a good long lasting gum and I didn't miss the popcorn or get thirsty. Then after doing that for awhile, I realized that I'm not buying their stuff anyway and would bring in my own can to drink and since I couldn't afford to buy the food anyway, they weren't going to be at a loss either way.
I've even had people working at the theaters notice me bringing stuff in because a few times I got lazy about hiding it and it was t-shirt, shorts, and sandals weather but nobody really cared that much that every pocket was bulging with goodies. If they did give me crap for it, I would stop frequenting their theaters because they are a dime a dozen now.
Now that high school is in the distant past for me, I've enjoyed going to theaters that have 21+ theater rooms and a liquor license. Their full service bar has prices that are similar to a bar and the fun part is I can get a few beers for the price of one drink at a different theater and they have bacon popcorn. I don't usually spend money at theaters often and go to a restaurant with wait-staff less than once a month and don't go to coffee shops or other pricey luxuries that mostly charge for a service and I do my own oil changes. Now if I go to a movie, I go to the nearest one that I walk to from my house early on Mon-Thursday when they have $5. I like to drink a little bit of alcohol at the theater and its hard to hide enough in to feel it and still have it be drinkable. I buy their slushy which is the same price as their standard drink and I dump my flask in. Now they get their concession and I pay the premium for watching a movie before its released in a cheaper venue outside the theater. This is usually only when I have a favorite actress in a movie or there is a must-watch movie and usually I use gift cards that I get on birthdays and Christmas so it doesn't cost me cash that I could send other ways anyway. For everything else, Red Box is $2 for a Blu Ray and I watch it using my 1080P projector($655) on a 95" piece of my wall that I painted with $20 or whatever for a gallon of Behr Silverscreen paint from Home Depot, the screen is effectively bigger than the theater and I have as much popcorn and drinks I want and can be social with friends without being rude to people paying big bucks. Anyway, here is the video of how we all felt when we were youngins' smuggling in the goodies from outside.
opcorn: