Starbucks, coffee, economics, intrigue, this story has it all! ;-)
Starbucks Economics - Solving the mystery of the elusive "short" cappuccino. By Tim Harford: "Here's a little secret that Starbucks doesn't want you to know: They will serve you a better, stronger cappuccino if you want one, and they will charge you less for it. Ask for it in any Starbucks and the barista will comply without batting an eye. The puzzle is to work out why.
Economics has the answer: This is the Starbucks way of sidestepping a painful dilemma over how high to set prices. Price too low and the margins disappear; too high and the customers do. Any business that is able to charge one price to price-sensitive customers and a higher price to the rest will avoid some of that awkward trade-off."