I'm glad you asked that! I don't pretend to be an expert, but this is what little I know.
I don't know how recent this has been. I think it has something to do with "reciprocity" fees. Since the U.S now requires almost anyone coming into the country to have some kind of a visa (for which they have to pay), in return other countries are imposing the same type of requirements on U.S. citizens. I don't think you actually need a visa to get into Chile. At least on our cruise (which leaves from Rio), the cruise line has said we can use our Brazilian visa (which cost $140.00 per person, plus service fees
to enter Chile. BTW - I worked with a very helpful visa service company in San Francisco, and had the visas within two weeks. In any case, while not requiring the visa, I think collecting the entrance tax is the Chilean government's way of getting their share of the tourism dollars.
Now, my question is: I've also heard that if you enter Chile by land or sea, but then fly out, you have to pay a departure tax at the airport to get out.
So, if anyone has additional information on how this whole thing works, how you pay, what currency, how much, etc. I (and I'm sure the OP) would appreciate your expertise.