There is a reciprocity entry fee per person if you enter Argentina through an international airport.
Canada and Australia passport holders are required to register and pay the fee on-line by credit card prior to arrival at the Provincia Pagos website.
United States passport holders are currently excempt.
A printout showing proof of the on-line payment must be presented upon arrival in Argentina or entry into Argentina will be denied. Also retain your proof of payment for any border crossings and re-entry if applicable. Once paid, it permits multiple entries into Argentina for the expiration of the passport in accordance with United States visa reciprocity.