In the past (decades ago), before the EU capped processing fees, I had pretty good success just asking for a discount when paying cash, even in supermarkets. A

In the past (decades ago), before the EU capped processing fees, I had pretty good success just asking for a discount when paying cash, even in supermarkets. And yes, "it can only become cheaper" has a much lower cognitive load than US style payments where the advertised price is just a lower bound.