Going to the Cinema
I'm a big fan of Tim Harford, the 'Undercover Economist' for the Financial Times and Slate Magazine. He also presents More or Less on Radio 4 - a weekly look at numbers.
Anyway, in his book 'The Undercover Economist' there's a chapter about buying food and drink in cinemas and railway stations. He explores the ways it's packaged as part of the experience of movie-going or train-travelling and because of their effective monopoly they can charge the earth.
For quite some time now whenever I go to the cinema or take a train I've been taking in a flask of drink plus various snacks. I have one friend who does the same. She and her husband smuggle an entire picnic (including sandwiches) into their local cinema. Nobody has ever noticed or told me that I can't do it - perhaps because it doesn't occur to them that people would do that.
It's a good way of saving quite a bit of money and still have the full experience of trains and cinemas.