In a lot of cases they’re not actually saving much money on these systems. They’re not cheap machines, require expensive outside contractors to be repaired, and also still require an employee overseeing them.

It might seem cheaper in the sense that one cashier can oversee 6 customers using the machines instead of serving one customer at a time, but most of the time, there’s only going to be one person checking out. The only time that 1:6 ratio comes in to play is during narrow periods in the day when the store is very busy, like around 5~7 when a bunch of people are finished with work and on their way home.

Perhaps it would save money if they were keeping every check out lane open all shift long without these machines, thus requiring 6 people who’s sole job is to stand there idly most of a shift, but that’s not what they did. There is a lot of other work that needs to be done in the store, straightening shelves, refilling empty slots from overhead, helping customers find stuff. So most of the time 5 of those “cashiers” would be going around the store doing that when things weren’t busy, and then just staff the registers during those rushes. Those staff are still there, doing other things.

The machines are actually more expensive but the margins are the same since they just raise prices to compensate. The real point of the machines is that they give management more direct control over the employees, since they can task them strictly to certain things and not have to worry about them getting pulled off ad hoc to staff registers. The additional cost is passed on to consumers, in a functioning market customers would avoid stores that raised prices to pay for the added cost of the machines, but since most stores do this, customers don’t have much of a choice.