Also important to note:

Germany is a car country: most ways to work, gym, etc in the average German city are done by car. Makes it easy to drive the extra mile to the cheapest supermarket.

Austria is much better for using public transport or the bike. In this case you won't make the extra way to stop at the cheapest grocery. And in the areas in Austria where people use cars population density is so low that not a lot of competition between supermarkets exists