Tienda Leon is a car service you can pick up at the airport and they charge 130 pesos for one way from EZE to the center to BAires
Taxi Ezeiza is currently charging 98 pesos.
Both are reliable.
I find that the Tienda Leon cars are nicer and the drivers usually nicer than Taxi Ezeiza. Personal opinion.
Tienda Leon also has a bus service from the aiport to a bus depot in San Martin and that is 40 pesos per person.