Gaucho -
Depends when you're flying, but if you know well enough in advance, you can usually grab a fare from EZE - MDZ on lan.com for around $200 USD.
I just priced a dummy fare out, EZE - MDZ, from 12 - 19 Nov, and it came out to about 126.000 pesos chilenos.
Not sure I'd cash in AA miles for a $220(ish) fare.