I just dont understand the excitement over using credit cards.
I've gone to the visa calculator site, and the exchange rate is like $342. Thats about 10% below the MEP rate, and certainly below what I can get through the services -even with their higher service fees.
It's just super convenient. Sure, for those that live in Buenos Aires long-term you would probably just exchange some cash and save but many people like me only go to Buenos Aires for work or short trips and you have to assign a value to your time. Time always = money. And the time you spend going to exchange the money along with the possible risks of something happening during that exchange. (Possibly getting robbed, followed to your apartment, getting counterfeit bills, etc).
For tourists this is a no brainer and makes it so easy. Sure, you can get a better rate bringing cash but there are a lot of risks of something happening to Cash vs. just charging to a credit card.
Credit card charges are effortless and easy to do and totally avoids having to deal with cash which has to have some value placed to it. I'm still amazed that the government was able to pull this off. It's clear to see with the volume of $ spent how valuable this is to people.
Plus this leaves no real "paper trail" in Argentina from having to have records of you sending cash all the time into Argentina. I don't honestly see any real way that Argentina would even know what you were doing in Argentina financially if you are using a credit card issued outside of Argentina. Western Union is definitely being tracked so there is that reason too.