It's blatant price-gouging. Any stock in the store has already been sold to them at an agreed price. They can set a number and make their set margin.

Updating prices after each delivery might make sense (if their procurement department is absolute dogshit at negotiating contracts), but updating prices throughout the day is just someone trying to see how hard they can push their margins to drain every cent out of their customers.

That's probably one of those toothless laws that can be easily bypassed on a technicality. Like, just say the shelf is for "storage" and not "display".

So with things like fish that can change day to day are they required to just update it every day? that sounds nice.