> no casual customer to my knowledge has ever seriously asked what proportion of their peppermint tea and scones pays for a café's rent

Furthering your café analogy:

• How many cafés do you think pay an annual amount + 30% of their revenue to their landlord, and may only use the landlord's payment system comprising of landlord dollaz

• Would consumers of a popular café be seriously concerned if their café were suddenly closed because they decided to accept cash directly?