Like with poker, don't play only by your cards, play too by the cards of the LL.
1- In case of a short term rental :
. If the LL doesn't renew the contract with you, he might have to wait a few weeks at least, if not two or three months, before renting again (those are the best cards for you).
. On the opposite, you taking the risk to have to move to a new place just to spare 2 US$ a day are his/her best cards.
--> You could mix those two factors and ask much in advance -for next time- if he/she plans to raise the rent then wait until the last moment before giving your answer.
I agree that what you pay is not outrageous, far from that, it's correct.
2- In case of long terms rental.
First a bit of my own experience. I've lived from 12/2003 until 02/2009 in a very nice penthouse on billinghurst x mansilla (border of Recoleta but outside the tourist ghetto), with 5 rooms, 110 sq. meters, 50 sq. meters of terrace, last floor (just God above, if he exists).
I started paying 1.200 pesos/month (+ very low expensas) and ended up paying in late 2008 3.000 pesos (with about 250 pesos of expensas = including hot water + gas).
That's far from the unofficial inflation but with time, the LL was always getting more hungry with the raises.
I had to leave at midterm of the contract for personal reasons but the LL wanted to raise again at 3.600 pesos at that time, arguing that those were the prices, she would have no difficulty renting it again and so on.
Well, it turns out that right after I left, she had problems renting it (remained empty for about 2 or 3 months, and the rent was finally settled at 3.300 with the new inquilinos).
I actually had difficulties getting my deposit back when I spent 7.000 pesos in painting again the whole apartment when I left (paint was not new when I entered, I wanted to act as a gentleman). Her discurse turned from white to black (likely the thing I hate the most about the Argentinean mentality and it's not often that I criticize Argentineans) and she was now telling me that it had been very difficult to rent and so own.
--> Lesson learned
The point where I want to get about long term rentals is that if in the first years after 2002 the rents raised quite rapidly, now they are raising following an asymptotal (not sure of the spelling) figure and it's insane to accept 20 % raises every year.
It also depends on the apartment (1 BR ? 2 BR ? 4 BR ? = different markets).
Here again, you should be playing by the LL cards : for them, having Americans or Europeans is -almost- a synonim of safety and this has no price!
Also, "on the paper" (well, this is Argentina, ok), the rental fees have to follow a specific index if I recall (too lazy to check the law now).
So, how to deal with that? I guess we have to get rid a bit of our American or European habits and act/think/speak like an Argentinean. If not, don't complain to be eaten alive.
Also, if you have a certain amount of money blocked on an account to pay for the rent, why not offering to pay one full year in advance. I know that some people will adopt a no-no attitude towards this posture but it makes sense. That's what I did for the house where I live now and I simply said that because I'll be paying one full year in advance, I should not be handicapped by inflation.
This is Argentina and it's a Latin country, therefore we need to speak, argue, at times raise the voice, speak again and take full advantage of the fact we come from countries where people are a bit more serious regarding such kind of contracts.
But all in all, if food & service prices really raise by 20/30% a year, rental prices are now raising by 10% or a bit more.