In Denmark there often is, things like localised sales the 4-8 times a year a specific store celebrates its birthday or similar. You can scan their PDF brochures but you would need image recognition for most of them, and some well trained recognitions to boot since they often alter their layouts and prices are listed differently.

The biggest sales come from the individual store “close to expiration” sales where items can become really cheap. These aren’t available anywhere but the stores themselves though.

Here I think the biggest challenge might be the monopoly supermarket chains have on the market. We basically two major corporations with various brands. They are extremely similar in their pricing, and even though there are two low price competitors, these don’t seem to affect the competition with the two major corporations at all. What is worse is that one of these two major corporations is “winning”, meaning that we’re heading more and more toward what will basically be a true monopoly.

Next step: monitoring the updates to those e-ink shelf edge labels that are starting to crop up.

The few random checks that I did on a few products as I was shopping didn't show any difference.

Either I was lucky or they don't bother, who knows