Coffee in Greece (as opposed to Greek coffee) costs around €4 per cup because, in short, it is not 'espresso'. No, this is not a circular argument. You don't drink coffee in Greece standing at a bar downing your cup in one and leaving.
Can you use US dollar in Greece?
Does Greece Accept U.S. Dollars? Establishments in Greece do not accept U.S. dollars as a form of payment. You will need Greek currency for cash transactions in Greece. In places that do accept physical U.S. dollars, such as hotels, using them may result in very unfavorable exchange rates or additional fees.