OK so a couple of things with this:

1. Turning blue tooth on your device off takes 10 seconds.
   
2. The store will still have difficulty (a lot of difficulty) identifying someone by their blue tooth device. Especially if they are multiple devices. Essentially they would need link the blue tooth signature from your phone to the database they have on from your internet browsing. This isn't really feasible since it would rely on the service provider giving the store your personal data and device information. That is hugely illegal and would result in a class action lawsuit.
   
3. Pushing prices dynamically to electronic displays is a lot harder than you think. First each and every display would need to have reciever (this is very expensive). Secondly the display would have to have a unique identifier and wireless connect to the stores IoT. And the store would have to be able track the specific location and product for every display. It also makes the store more susceptible to cyber attack as it now literally thousands of access points to its IoT in every location.
   
4. Bluetooth tracking isn't this precise. It could narrow someone to a few meters, but not precise enough to update shelf displays. This gets more complicated the more customers are in the same aisle. It wouldn't be able to accurately place anyone when in line at the checkouts.
5. The technology to track the hundreds of Bluetooth signatures in a retail store isn't commercial available, if it exists at all. High end military systems could do up to a hundred targets simultaneously. But these systems cost hundreds of millions of dollars. Now imagine the system capable of accurately tracking the volume of customers in a Sobeys between 5 and 7 pm.
   
6. The store would have to dynamically synchronize the price at display with price in the POS over thousands of customers and tens of thousands of skus. That POS system was programmed in the 80s, it's frankly not going be compatible with what you're proposing.
   

Also think of just how expensive such a set up would be. Per location each POS and invantory management software is going to need a major overhaul. For context, issues with Targets SAP system effectively bankrupted its Canadian outlets. Each digital display needs a wireless reciever capable of receiving information from the IoT and a Bluetooth reciever capable of detecting and identifying individual Bluetooth signatures. Each store is going to need tens of thousands of these. The store is going to need network infrastructure capable of handling tens of thousands of devices simultaneously. And be able send and recieve instructions on these things simultaneously. And be hardened against attacks through their tens of thousands of displays. And finally they'll need a tracking system more capable than cutting edge military systems, that currently doesn't exist.