I'm sure if "shaken" is written in Italian that'll attract some business.
I don't know about Starbucks, but in traditonal tea houses, "shaken" means shaken with a mixtrue of milk and sweetener.
Also, the sweetener that costs you an extra few pennies is such because it is in liquid form. Therefore you save effort of not violently stirring in small packets of sugar which may or may not dissolve in your massive 24 ounces of 33 degrees iced tea.
Why are you so quick to call arbitrage? These are equilibrium prices, after all.
Price discrimination. The great game...how to get those people who will pay higher prices to reveal themselves.
Chapter 2 I think in Tim Harford’s "The Undercover Economist".