That's not so bad really. Fast food joints charge about that much for a soda, and they put so much ice in them you usually get about what you'd get in an airline cup. Food prices on airlines have always been ridiculously high.
In this case it's a simple matter of not ordering a soda. The things that really get under my and others' skin is stuff you can't avoid by patience, stuff like fifteen dollars to check a bag, TSA security goons making up the rules as they go, and it seems we'll soon be paying extra depending on body weight, literally paying by the pound for travel like we're really just a piece of meat to them.