Argentina's currency black market is just an acknowledgement of the actual price of the Peso that countries in the border have. You can LEGALLY exchange 1 US dollar for about 10 ARS in Uruguay http://www.bcu.gub.uy/Paginas/Default.aspx
It's caused a major disruption of commerce here in Uruguay, lots of people go to Buenos Aires to buy stuff (mostly clothing, etc).
My girlfriend studies in Buenos Aires because it's cheaper to take the ferry and pay courses in Argentinean pesos than to pay the course in Uruguay ! (plus, Buenos Aires is a much larger city and has a better selection).