How do you know?
I just take an example from Super Pola here in Sosúa.
I personally know some of those who work there.
The "bag person" (what a nickname

), can sometimes be a cashier, the security guard, someone who does something else.
And just think of it, at the bigger supermarkets, if just one "bag person" attends 100 people during one day and everyone in average gives him 25 pesos.
That's 2500 pesos, tax free. Then if he works let's say 6 days a week, that's 60000 pesos per month.
Do you think a cashier makes 60000 pesos/month?