from my experience for a large piece it's kind of nice to get a quote for the whole piece rather than an hourly rate, since frequently the hours get estimated and can easiy go well over the allotted time. That said, whether the price is high depends on the complexity of the design, how much you're asking for them to do (do you already have your design completed that they need to just draw out, or do you need them to adapt/change/or otherwise help you 'realize' your idea), plus their sheer level of artistic skill. Obviously the higher quality artist they are, the more they will charge.
For me, I wouldn't think about whether $2000 pesos is expensive in Argentina, but whether $2000 is expensive for a piece of art that you will have for the rest of your life covering half of one arm. You will see it every day for the rest of your life, and you better like looking at it!
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I know in Seattle, for example, a $500 half-sleeve would be a steal. That said, without knowing what your design is, personally I would consider personally $2000 pesos or $500 dollars to be a relative bargain for what will most likely be a minimum of 10 hours and maximum of 30 hours of tattooing but ** IF ** and only if your tattoo artist is highly skilled and can deliver the outcome that you desire. That said, definitely shop around! While you don't want to be cheap about your tattoo, you also don't want to get ripped off. That's one of the turn-offs to me about Bond street--they are "the" spot in town and so I think any clients are generally taken less seriously because the artists don't have to work for clientele. It's reminds me of the Hot Topic of tattooing (although I'm sure there are some talented people working in there). I bet that not being taken seriously (and/or being taken for a ride) is especially true if you're a foreigner.
I have a friend who had a nice piece done here, I'll ask her about the shop and pass on the info to you when I hear back if you like. In the meantime, here is a link to an Argentine tattoo magazine that likely is a very good resource:
http://www.pielmag.com/index.php?sec=1
Good luck and enjoy the process!