Fizzy sodas served in pint plastic tumblers full of ice are standard restaurant fare here. It's always "all you can drink" for one price, and there's a reason for that.
The ice costs about 5 cents per glass, the C02 for the fizz about 3 cents per, the water about 1 cent, and the syrup (Pepsi, root beer, etc) about 15 cents.
And they charge, on the average, $2.25 for it. Even with paying the waitress (and they only make about $3 per hour from the restaurant, the rest is in tips), it's about a 1000% profit on those things.
Beer or lager, I suppose, is different, but I'm not familiar with that.