Tim Harford explains:
The UK’s Office of Fair Trading (OFT) has been turning to behavioural economists for advice on such tactics, and has found that there is no pricing scheme more pernicious than “drip pricing”. Under the scheme, customers agree to pay a price only to discover that there is a charge for delivery; another charge for paying by credit card, and another for insurance. Drip pricing taps into the endowment effect, because customers feel that they have already made the decision to purchase; it creates loss aversion because customers commit time and effort to the search before being hit with extra charges; and it is a form of complex pricing which makes it hard to compare offers.
Hat tip: Simoleon Sense