Off the bat, it's probably more that they will save on the materials and labor of having to send out reams of tags to every store in a company every week, and having employees come in, usually on 3rd shift, to swap tags. Having spent a lot of time working in a grocery store however, I can guarantee that these will malfunction regularly and most employees won't actually be trained in how to fix them.

Down the road I tho, "surge" pricing seems inevitable. Also raising prices based on inventory on hand. "Oh that item is twice the price because it's the last one left, sorry."