Checking the USD to BRL rate is one thing; sending money is another. Grey adds three costs to a transfer, a deposit fee, a conversion fee and a send fee, and shows every one of them with the exact real amount your recipient receives before you confirm.
Take a $500 transfer funded by ACH: the deposit fee is about $4 (0.8 percent, minimum $2, maximum $10) and the conversion fee is $5 (1 percent, capped at $6). The send fee is listed separately, and the exact real amount for Brazil is shown before you confirm.