[marc_taler]

I've never been in a Costco - is that a mall where you pay in each shop individually, or a single store where you pay the total at the exit? In the latter case, the customer is legally only buying from one merchant, who can of course decide which payment system(s) to accept. But in the former case, in the EU it would be illegal for the mall operator to dictate which payment methods shops may offer their customers.