Is there anything stopping merchants from offering different prices to people based on different payment methods?
I assume the reason merchants do not list a discount for paying via SEPA or ACH or debit card or whatever local non credit card (and non Visa/Amex/MC) option, is because merchants benefit from the higher prices that people are willing to pay when using credit cards (compared to the cost of accepting credit cards).
In the US, Target is the only big retailer I know that discounts for using ACH (debiting directly from bank account). They give 5% off.