Friends of mine, husband and wife, once argued over the price of a branded packet of lemon slices bought at some convenient corner shop or petrol station. She complained that the slices weren’t worth the price she had paid. He pointed out that she had bought them – albeit grudgingly – knowing exactly how they tasted, and that therefore they had to be worth what she had paid. No prizes for guessing which of them is an economist.

We economists know a lot about pricing, but we tend to be baffled by the way the rest of humanity thinks about it. The package holiday offer, “Kids go free to Disneyland”, is, to an economist, a profitable attempt to charge more to couples with two incomes and no children, who are likely to have more cash to burn. To everyone else, it is an idea waved through unquestioningly.