Disclaimer: I am more or less pulling this numbers out of thin air.

Assume that having a single cashier costs $15 per hour. Assume that an RFID tag costs $0.05. Assume that in average a cashier handles 1 item for only 5 seconds (including payment).

That means that a cashier can handle 720 items per hour, and that costs the supermarket $15. Having RFID tags for 720 items would cost $36. That's still a ~$20 dollar difference, which still amounts to ~$0.028 per item.

I would be willing to pay that if that means i can forgo the checkout lines.