[rightbyte]

It is probably quite common for people to put items in the bag after failing to scan them by mistake. But I guess an "a new item check" which is not very weight sensitive would be enough to counter that.

Self-checkout works best in Home Depot type of places in my experience. There are just so many items to keep track of in grocery stores.

[oneeyedpigeon]

Combine the low frequency with which that must happen and the money they save by replacing a worker, and you'd think they could just write that off.

[devrand]

They probably are writing it off anyway. I've never had an employee actually check -- they always just scan their barcode and clear the error.