In a way, they are being more truthful about the costs of the goods, and then the cost of the payment method you chose to use. However, people don't like to see this transparency as they feel like they are being overcharged.
Many other suppliers will have a slightly higher goods price to average out the varying costs of the payment methods their customers chose to make, and then don't pass the charges on. You may find that if you pay in cash you get it cheaper at those places that are transparent with their charges, where as if you want to pay by a more expensive payment method then it will be cheaper elsewhere.
But yes, the simple answer is to look at the total price of the product and then buy it from the cheapest place. Capitalism at it's finest!
@ jxk - I don't actually agree with charging for the use of the debit card. Aside from processing the transaction which is done automatically, there is no associated cost for the bank. At least no more so than withdrawing money from an ATM, paying over the bank counter, or sending payment via internet banking, all of which are charge free. In fact, one could almost argue that it's cheaper and more convenient for them.
I do, however, fully accept the charges for credit cards. Not only should people be discouraged from using them and falling in to the debt ridden mess this country already is (just ask my wife
), but there is also the question of fraud insurance etc that you get with credit cards which has an associated cost too.