I don’t know what the fee request is at present, but if it is R$100, then don’t worry, for with the exchange rate being as it is, that is not much money at all. Don’t expect to pay what the locals pay, for the guys at the saunas don’t expect to receive from a tourist what he receives from a local.
When I traveled to both Rio and to Sao from 2002 until 2011, I paid no more than R$100; I did not do any overnighters.
Read the other threads regarding fee requests at the saunas in Brasil. Also, note the economy in Brasil has tanked, and if the quoted fee is R$100- R$150 plus, negotiate. The final, agreed to amount is the guy’s choice.