Idk about Europe in genera, but in France you cannot have different prices for cash/card. There can be (and often used to be) a minimum amount to pay with card, but that's it.

But do note that card fees are capped at 0.3% max for credit cards, so negligible in the grand scheme of things. Banks used to charge an arm and a leg for a terminal though, but a bunch of startups like SumUp broke that oligopoly and even random small stands in fairs propose card payments via them "for free".