how do people make money?

the local AZ is likely just a hub/fulfillment for a variety of orders/venders/sellers

AZ gets massive discounted wholesale on jug, ebayer gets jobber on jug, 3rd party ships. everybody gets a piece of the pie.

dude in VN makes 2 bucks, 5 bucks or whatever for doing literally nothing, AZ makes 8~10 for just having what they were gonna have in stock anyway and they don't care who they're selling to, shipping makes their nickle and completes the cycle.

the receipt is probably just a glitch in the system. everything has to have an invoice or paper trail to track sales/inventory and so that just gets printed off at the terminal. there's probably a part of their process in budget reconciliation that accounts for it, but to simplify the transaction they just print it off this way.