If there were real competition then electronic labels would be just fine. One company would try it, another would stick to fixed prices, maybe another one would encourage people to bargain on everything like ye olde days. Some people might like dynamic prices because they thought they could game the system. I certainly love picking up things in a store that are discounted.

For that kind of thing to work, you’d need at least 5 or 6 truly fully independent grocery stores that are convenient, viable options for people in a certain area, and probably 10+ in a wider geographic range for people willing to travel a bit. Instead we tend to have 2-3 companies dominating all grocery business because anti-monopoly laws are no longer enforced.