Generally speaking peak season for coach/leisure travel is low season for business demand - so this doesn’t bode well for the flight. In the Northern Winter, Argentina flights should be printing cash as its summer down south. If peak season coach fares are being discounted and sold sub $1000RT, I think that raises some red flags....
That's a true fact within the same hemisphere because is the same season in both ends of the route but I'm not so sure about this north-south hemisphere routes. The timing of "peak season for leisure travel" depends on where do you originate.
I have never checked but I won't be surprised if a US-EZE-US is priced significantly different that an EZE-US-EZE depending of seasons.