I was forced to make an ATM transaction (in order to activate a new debit card) lately and I was pleasantly surprised that it was not as expensive as I had feared (I usually cash checks at a cambio - this was the first time in almost eleven years that I used an ATM here). I used the Ban Reservas ATM at the POP airport and was charged $2.00 by my foreign bank, a 13 cent international fee and nothing by Ban Reservas.
Of course, all I withdrew was 500 pesos in order to active the card via a PIN transaction.