In Norway there is already a low fee processor called BankAxept. It has made it practical for shops to sell even the cheapest item and accept payment by card without losing money.
This seems to have happened in the UK now too, though all bank debit cards have been Visa Debit since 2009 or so. I think fees are now solely percentage based and close enough to bank cash handling fees that there's no longer any downside to accepting card payments for small transactions.
https://en.wikipedia.org/wiki/BankAxept