Apparently UK supermarkets sometimes advertise deals that charge prices higher than the usual, listed price:
In the worst cases, Which? found that supermarkets doubled the shelf price of an item when they began promoting it as a money-saving multibuy. It found that Asda was selling a Goodfella’s Deep Pan Pepperoni pizza at a standard price of about £1, but when it went on to a multibuy deal, the price jumped to £2.50 for one or £4.50 for two.
What is conspicuously lacking from the report is the percentage of advertised deals that do not involve a saving. Mistakes happen, and there are plenty of ways in which a listed price could dip below the deal’s price if supermarkets regularly adjust prices. If only a few dozen examples of this could be found across the tens of thousands of deals that supermarkets advertise every year then I’d be tempted to chalk it up to errors, rather than devious pricing strategies.
Of course, it could be that supermarkets are systematically taking advantage of our decision heuristics, which would be far more exciting