all they have to do is add more sugar to make up for the missing hazelnut
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For Nutella specifically, there are also differences in composition between the more wealthy European nations: https://www.youtube.com/watch?v=CXp2MTWNoZ4 According to that report, the texture is different to accommodate for the differences in common bread types, which makes a lot of sense IMO.
With how little actual hazelnut goes into a jar of Nutella compared to palm oil and sugar that make up most of the spread, I doubt Ferrero is saving a lot of money selling inferior product to poorer countries. With expensive goods such as meat and "pretty" vegetables, there's more money to be made.
In my circles such mutterings would be seem as populism and woowoo crap.