Visa is one of the largest card issuers in the world. Here you can find the most recent Visa Interchange tables showing the cost to the processor for each card type. You can see that there are many cards and the rates start at 0.05% and go up to a 2.95% cost. There is also a per item cost on each card type that is generally $0.10 for credit and $0.21 for debit. Many merchants do not completely understand interchange fees and educating them can give you a foot in the door but first you need to learn them for yourself.
Click here to access the interchange tables for Visa in PDF format.