I've been teaching for 2 and a half years here, and I recently upped my price from 80 pesos an hour to 90.
I'd be surprised if a decent teacher can live comfortably, independently of other income, and maintain a high level of teaching for much less than that. 100 doesn't sound unreasonable to me, given that two and a half years I was advised by experienced teachers to charge 80. With inflation that would probably be about 120+ now (I'm not a maths teacher).
I know Argentine English teachers who are charging the same and more, yet their English isn't perfect. Don't forget: if you're a qualified native teacher with experience here then you shouldn't undersell yourself. You're able to offer a premium service and should be compensated for it.