You buy something worth more than 300 USD abroad and are a resident of Argentina --> when coming back to Argentina you have to queue in "Declare" instead of "Nothing to declare".
If you queue in Declare you have to pay 50% of the value over 300 USD.
If you queue in Nothing to declare you might be randomly checked and if found at fault your purchases will be confiscated.
While it is easy to buy clothes, use them and pack them, for electronics good things are different because you should be declaring your imported goods upon LEAVING the country. There is an AFIP form where you have to state make, model and serial no. of your phone.
For example, I have an iPhone 5, I travel abroad and decide to buy a iPhone 7. In this case I have to declare my old iPhone 5 upon leaving Argentina.
When coming back with a new iPhone 7, I will have purchased goods for over 300 USD. Assuming an iPhone 7 costs $1000, when I travel back to Argentina I have to declare it (show purchase receipt). $1000-$300 =$700. A 50% tax means $350. So I will end up paying the phone $1350. Might as well buy it in Argentina.
Even if I declare I exited Argentina with an iPhone 5 with serial no. XXX, they'll see I am entering with an iPhone 7 with serial no. YYY. The only thing that comes to my mind is if I have someone buy the iPhone 7 for me, pass me the serial no., declare that serial no. when EXITING Argentina with the old phone and hope they don't check.
The limit is just 150 USD if you travel by sea or land, btw.
So much for the Paris of South America.