I understand what you are saying but my monthly bill would be pretty much the same whether i had an iPhone or some other smartphone so I really don't include my monthly payment into the equation. Its a constant whether on a contract or not or have an iPhone or not the payment would be the same so whats the difference?
I'm talking about if you were to buy a SIM only contract deal (they are significantly cheaper in UK, e.g. £10-£15 less for the same plan but minus the phone (and 12 month instead of 24 too).