The United States charges a large fee (about $160) for issuing a visa to citizens of Argentina. In response, several years ago the government of Argentina began collecting a fee of the same amount to Americans. They called it a “reciprocity fee.”
Now Argentina has suspended collection of the fee.
http://thegate.boardingarea.com/argentina-visa-reciprocity-fee-suspended-for-american-citizens/
Argentina recently installed a new government, much more friendly to the United States than the previous one. It’s likely that this fee-suspension is related to that.