Hey, On The Brink.
I'm currently charging between $21,000 - $26,000 per hour for a 1-on-1 class. In part, what I charge depends; for "conversation" or relatively simple "apoyo escolar" classes, I charge less, while if it's something like IELTS/TOEFL prep or for ESP, it goes up.
I'm finally getting comfortable charging higher rates, in part because many of my students come to me via my teaching website, others are through word-of-mouth recommendations. In terms of my professional background, I've taught ESL/EFL more than 21 years. BA in secondary education and Spanish, MAT in ESOL from a US university.
I'm hoping in the future to be able to charge more (not just in Argentina) when I am more specialized in my specific niche (i.e., working with students with special needs). I've learned over time that it's not just a TEFL/DELTA certificate, nor "native speakerism" that makes a teacher worthy of charging a higher rate; it's their USP (unique selling point).
Just something to consider. Suerte!