However, in my opinion the major reason for the price/quality imbalance is less competition and higher costs due to less developed/more expensive infrastructure. For example, around my place in Germany there are 10-15 or so big "grocery chains"

The competition in groceries in Germany is close to none; low level chains sell the same products for the same price. I dare you to find a difference between the bread sold at Aldi and the one from Lidl. Same with milk, eggs and other basics. Same quality, same price, down to one cent.

BTW Ten grocery chains? I can't even name that many in Germany. Where do you live?

fighting each other for more or less the same customer group (people with low to normal income) which is higher than I ever saw in East Europe.

The chains are not fighting. This is not competing, but almost a cartel.

However, don't think that "different stuff for different countries" only happens in East Europe. For example, Lindt produces different chocolate quality for Germany than for Switzerland.

Didn't know that. Any other differences?