It was possible for many decades already, budget and maintenance-wise. You can at least accept a credit card as an alternative. Yes, it's not perfect, but the fully digital alternatives also have drawbacks, as pointed by OP.

I know but you're fighting the cost difference between installing CC terminals and QR code stickers.

Things that were possible become impossible. Once Britain ruled the seas with wooden sailboats. Those boats are not perfect but could they win today’s naval battles? Also no.