Can you share them? I recently looked for such projects and didn't really find anything that works well.

The issue is that each market sets their own prices and I believe REWE is the only large one where you can fairly easily scrape the product catalogue. I thought about it in a shopping list context, so you'd need to make it location dependent to be useful. But you could do a lot of cool things with it. Like choose a basket of goods and it creates a route for you: "Go to supermarket A and buy goods XYZ, then to supermarket B and buy ABC"