I think the point stands: the amount of complexity involved in each little piece of app is huge when taking into account dozens of countries and customizations

I think the point stands: the amount of complexity involved in each little piece of app is huge when taking into account dozens of countries and customizations by city. If it still doesn't seem worthy of 'thousands of engs', imagine breaking down every point in the list to the level of detail the author broke down payments. And then apply the logic in the top comment mentioning backend systems + teams to support other processes (and internal tools needed). Edit: sorry too much caffeine got me edgy.