When booking online....

and presented with a set of options, each of which comes in Expensive flavour and Cheap flavour, with the price for both Expensive and Cheap marked next to every box, WHO in the name of little green chickens clicks the Expensive box without looking at the price, clicks through to the next page, clearly marked as Expensive flavour, finishes the transaction, and then several days later, phones the merchant to complain that, actually, they didn't want Expensive flavour, they wanted Cheap flavour.

The boxes are clearly separated, the only way they could be making this mistake is if they aren't actually looking at the prices at all!

I now understand why email scams do so well...