This was only an experience one time, but I was waiting in line to checkout at Walmart and listed to the registers's beeps. I could hear about one beep per second from 3 or 4 registers combined. (all the ones they had staffed.) I could scan faster than a single register that day.

That being said, I hate the turn to self checkout. A conglomerate like Walmart has no excuse to not pay and staff properly. Or give me a discount for providing my labor.