I'm going to wager this is because people in Argentina tend to make less money if the World Bank's stats on GDP per capita are to be trusted. In 2013, the GDP per capita of the United States was 53,041.98 USD. For Argentina, this figure is 14,715.18 USD.
The average American is making over 3 times as much money as the average Argentino per year. The costs of living are naturally going to be higher. That being said, things are still overpriced, but I would expect Argentina to be much cheaper because people overall earn less.