For the average German retailer it's around:
0.23% EC
0.5% Maestro/VPay/MasterCard Debit/Visa Debit
0.8% MasterCard Credit/Visa Credit
2.5% Amex
But of course that depends on the size and the negotiation skills of the retailer. I'm always envy when visiting the Netherlands, "PINNEN ja graag" signs everywhere :)