Really? Please pass me the name of your incredibly cheap cab driver, because I took a cab from Puerto Madero to Las Canitas (which is halfway across town -- last Thursday night at 930pm, very little traffic since it's summer and it cost me 60 pesos -- and his meter was not ticking up in any untoward way. From Las Canitas to Caballito (again, about halfway across town) it's about 45. And late night, even more. For $4 (which even if you're using rate of 7:1 is 28 pesos -- I'm assuming you're talking USD since 4 pesos won't even get you in the door of the cab) you can get from Las Canitas to Recoleta if you don't get stuck in any traffic at all.