Just remember that negotiation is often an option if there is more supply than demand! Last week we took a taxi back from EZE (to San Telmo) for 100 pesos including tolls. Outside the sliding doors there is a yellow taxi stand on the left. When they asked if we wanted a taxi I said, "No, it's too much" and they asked how much we wanted to pay. I said $100 and they said ok. Sure, $100 isn't the $4 pesos for 2 scenic rides on the #8, but it's also not $150. My apologies if this doesn't help the OP, but perhaps upon return!