Correct, but crosstown fare, airline fare and fare at destination shouldn't even get close to AR$2000 (the ex-AEP airfares are AR$942, and that's in premium economy; I don't know how much my current remise charges between EZE and AEP, but I'd be surprised if it's more than 600). Going by private car will be two if not three times as expensive. But the flight schedules being limited as they are, it still may make more sense, as getting a car just to pick up and go to Rosario will undoubtedly be faster and less hassle.

If, on the other hand, the OP wants to have a nice lunch in Capital Federal, and then fly along to Rosario on Aerolineas in premium economy afterwards, he could easily do that and still have as much as a few thousand pesos left over compared to the cost of hiring a remise to drive him.