We know that intercity demand in ASW is based largely on population within a certain range of the airport. The details are not super important for this post, because the numbers for Buenos Aires are so far off that I don't think they matter.
Here's the thing: Buenos Aires is the second-largest metro area by population in South America, with around 15 million population. So we would expect the overall demand for airports in the metro region to land somewhere between that of airports in the largest metro area in South America, Sao Paulo (22 million), and the third largest, Rio de Janiero (13 million), probably closer to Rio.
Let's do a benchmark. We'll pick a point pretty close to equideistant to those cities...Cali, Columbia (CLO) is 2883mi from EZE, and 2878mi from GIG. Since Buenos Aires is slightly bigger than Rio, we'd expect slightly more demand. Actual demand from CLO to GIG is 11,881, but actual demand from CLO to EZE is only 626, less than 5% of demand to GIG.
So, we have equal distances and equal populations, but maybe language or culture or something is factoring in? Let's compare EZE to the main airport of the next biggest Argentine city, Cordoba. Cordoba is about 1/10 the size of Buenos Aires, with a metro area of around 1.5 million. Again, we'll pick an equidistant city, Fortaleza, Brazil (FOR), 2492mi from EZE and 2526mi from COR. Actual demand from FOR to COR is 442, and actual demand from FOR to EZE is only 172, so demand is 1/4 for a city 10x the size.
Well...maybe EZE is in a bad location? First of all, well, NO, it's not, it's smack dab in the middle of the greater Buenos Aires metro area:
Second, Buenos Aires is a big city, and it's served by multiple airports. So, let's check them all from some big hub, like JFK. JFK-EZE generates 2,111 demand. JFK-AEP generates 2,069 demand. And EPA, although it has commercial service, isn't represented in game (but there's another thread for that).
Again, compare those numbers to Rio, a slightly smaller and closer city (GIG: 40,767, SDU: 40,406) or Santiago, Chile, a significantly smaller and further away city (SCL: 19,788), and it should be clear that there's something very wrong with demand in Buenos Aires.