It has been more than 40 years since I majored in economics at a first rank school, but I still understand the basics of supply and demand. What I don't understand with regard to UA fares to/from EZE is:

Why should the South American routes be less profitable than other domestic and foreign ones? (Are domestic routes and foreign ones separate discussions for one or more reasons, e.g., different fleet requirements, the need for even non-profitable domestic feeder routes, the costs of maintaining a ground station, etc.?) Are the economics of the EZE routes comparable for the GRU ones?

Are the economics for UA to/from EZE better (or worse) now than when they flew out of MIA and to SCL?

Is there something of a cartel on flights between EZE and the States, as I believe there is on flights between Australia and the States, keeping fares artificially high? What is the story as far as service and fares with other carriers providing non-stop service between EZE and the States? (My interest is primarily IAD-EZE and only infrequently have I looked at non-UA fares out of other cities.)

Why are UA fares to EZE from the States so much more disproportionate in comparison to those to and from Europe than they were 5 years ago?

Presumably, knows its business better than any of us, especially where fare setting is concerned. But rather than just hear it is a matter of supply and demand, I would love to hear what is particular to the EZE routes, especially the IAD-EZE ones. They do add seasonal service on those routes, don't they, so why not add some more as long as the demand is there?