I read about a different theory. Supermarkets like fastfood restaurants like consumers to buy what is most profitable for them. They will make certain options more expensive and some options like upsizing appear cheaper.

So supermarket A will sell Coke and its own storebrand cola. Naturally, the Coke will be more expensive than the storebrand cola. However, another supermarket only carries Coke might want to price their Coke at a more affordable price.

Secondly, some countries do use different packaging for things they sell in different countries.

So when Johnny foreigner goes to a local supermarket, he is not their target shopper. He might not recognize the storebrand cola. He also may not want to try the storebrand cola. He also may not recognize Coke with a different packaging or language label.

So he is stuck with international brands that do not bother to change their labels. Even for things like potatoes, some countries that do not have potato as a staple might use expensive potatoes to direct their regular customers to the native carbohydrate.

Lastly, when Johnny foreigner from wealthy looking country asks for directions in the supermarket, nobody is going to direct him to the discount bin.

When I cannot understand or read the local lingo, I often get charged an arm and a leg for the international brands.