Surge pricing really only works when you put the customer in isolation. Uber can do it because you're the only one seeing the rate for the trip you want to take. Amazon can do it because you're shopping while taking a shit at work. Nobody else sees the prices in your online shopping cart, that's not the case in retail.
The profit motive behind these tags is wage savings. It saves in the time it takes to change out price tags when the prices do change. It saves in the time used in finding and replacing missing or damaged tags. It saves in the amount of manual price corrections at the till when the tag doesn't match the till because the tag wasn't updated - or the lost time and revenue if someone abandons their cart because of said disagreement.
Could they do what you're saying? Technologically speaking, it's been possible for several years - we've had these tags on most major store shelves in Canada for a very long time now and apps tracking our every move. Why hasn't it happened already? These stores have had everything they need to implement this scheme, and of all the shady cunts in this world, Galen Weston would have by now if it could have turned a profit.
It's easier to just price-fix the bread and pay a fraction of your profit in lawsuit settlements decades later than to do what you're describing.