PAYG have minimum top up and contracts are fixed fees... just like line rental. why dont people see this is the same? eitherway, you are paying to maintain and upgrade a massive infrastructure, not simply a cable from you to an exchange (or connection to mast).
in the opposite way, petrol round Eastbourne has always seemed to be 2-3p cheaper than elsewhere in East Sussex, for no reason that i can fathom. also, BP garages typically charge 2p more than nearby branded garages. neither of these can be explained by supply/demand, the petrol market must be...