The companies won’t pay the 10% out of their own pocket, as they most likely couldn’t. At least here in Germany, supermarket margins are pretty thin.
This doesn't pass a quick reasoning check:
- Self-checkout machines cost the store capital investment (they introduce some new technology, there is a larger number of devices)
- Self-checkout machines cost the store operating budget (more devices means more parts to be serviced)
- Stores have added significant numbers of self-checkout machines
So the stores must be getting better margins at self-checkout than at human-checkout, or they wouldn't introduce it.