Aerolineas Argentinas has round-trip flights from New York (JFK) to Buenos Aires (AEP) for $652, NONSTOP. Flights August to November. Departures on Tuesday, Friday, and Sunday. No Thanksgiving dates.
Some small OTAs on Skyscanner and Google have this for $569; cheaper than the airline. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.