There doesn't need to be a cashier. If there was a wall of touch screens, and all the food production was automated, you'd only need unskilled labour. Cleaners,

There doesn't need to be a cashier. If there was a wall of touch screens, and all the food production was automated, you'd only need unskilled labour. Cleaners, and someone restocking the food inputs. You could have someone service the machine once a week, or in emergencies - but they already have expensive machinery running, so they probably already have the support staff infrastructure for those jobs.