Games are marketed at different places depending on your country of residence. Usually they take the source of payment as proof of residence, i.e. you need an Argentinian card to pay if you want to get Argie prices.
However, I think in Steam you need an Argie account to keep accessing your Argie-bought games. So you'd have to switch between accounts from different countries to get the best deal in games.
The price difference can be 50% or more if there is a parallel currency going on!
I remember that a decade ago I checked these prices and the Russian prices were 50% less than the European prices. However, you'd need a Russian account, and everything was in Cyrillic thereafter.