As to the prices, they seem crazy out of line. I'd expect fares in main cabin to be max $1500-ish.

I would expect prices on this route to be relatively high, but not that high. Argentina is a popular tourist destination, even more so with tourists and remote "workers" all trying to take advantage of currency arbitrage. It seems that, post-pandemic, prices to traditional business destinations, or even places without a huge tourist demand, are dirt cheap, while tourist destinations are at least 50% more expensive than in 2019.