Guys.....lets do some math here, so that everybody understand why the dollar is more worth than the CFK quote:
You are allowed to enter this country with 10.000 USD un-declared
(If you declare you can enter with more)
So, today we have an official dollar rate at 4.46!
The under the table rate is, in this second 5.20, (just checked where I normally sell dollars).
Thats a 16,59% difference between the official rate and the black rate!
If you enter this country with 10.000 USD you get 1659 USD more for your dollars than if you would go to the ATM and withdraw the dollars, (in pesos!), from here!
So, now you go to a travel site like Despegar and look what a ticket to USA or Europe cost! Then you will realize, that with an amount of 10.000 USD, you would pay for your flight and even have some hundred dollars over if you brought the money with you cash! (or have a friend or relative or whatever, bring it)
If you do this calculation with the true value pesos you get out of machine, which is around 4.20, this hole story makes you 23,80% or 2360 USD!
Therefore: Even that 2 Americans transfer larger dollars between their accounts outside of Argentina, the peso BUYER would be more than stupid to accept the 4.50 rate! (assuming we talk larger amounts as is indicated in the original post).
This is the reality, sorry!