For our 50m2 (+ 30m2 patio) in a 5 y/o Caballito torre that has somewhere around 50 apartments, we pay anywhere between 250-400 pesos in expensas per month. The encargado is ok, but mostly seems to get paid to stand around in front of the building, sweep the lobby and take the garbage out daily. There is a (small) pool and SUM on the terrace. Oh well, now I can see from the rest of you that we're not paying quite as much as some of you--I can't imagine forking over 1k pesos a month just in expensas!
If I were to buy I would also not consider anything other than a PH or a smallish building without a portero.