I am not aware of an offical govt policy to charge non argentines more. i just went on the aerolineas argentinas website and went thru the reservation process for an flight within argentina. i was not prompted to reveal my nationality. my wife is argentine and we have traveled extensively throughtout argentina and we have never been quoted two different prices. there definatley are shady travel agencies that may attempt to charge more, but i have never encountered the dual pricing policy booking my tickets thru the web, in the airport or an the actual airline counter.
In have been to countries where an offical dual pricing policy was the norm, china and vietnam in the early 90's did this. it was a nightmare for the govt to manage and opened the doors to a huge black market. because of this i highly doubt an offical govt sponserd dual pricing policy exists in argentina. i think the problems reported on this forum are as a result of bad travel agents.