We in Zimbabwe know a thing or two about running on cash only. Been doing it for almost a decade.
Prepaid cell phones can be topped up by buying a code at a Shoppers for cash. Even your hydro bill will take a money order if you have cash but no bank account.
Having said that, almost every time I pay more than 20 in cash, the seller gives me the eye, puts the money under a UV light, and I feel like some sort of a criminal.
Only once has it resulted in them calling a manager over. Every other time, it gets strange looks, a chuckle, a smile of mirth, or a groan. Either way, it's something unusual for them to hear in what is likely a repetitive job.
I assure you that quip is not unusual in the least, just another repetitive part of the job.
I am assuming there's some good with the bad.