I used to by all my PC parts from a shop that had a 5% discount for cash purchases. It was the sort of shop that was just a counter with all the merch hidden in the back. I don't know how they kept the CC companies from knowing but maybe 40% of their business was cash purchases (circa 2019).
We must be very different consumers.
Also, many places already do effectively this, they charge a surcharge for using a card.
It used to be here in the US, but there was enough violations that they stopped putting it in the terms.
But, looking into this, it looks like some states have made it illegal. I'm curious how well that's enforced.
For those on the other side of the balance, maybe it would be.
Either way, I can't imagine many shops doing it, even if the economics makes sense. They'd rather the immediate and direct pad to the bottom line.