Between individuals it is free. For commercial transactions, there is a fee between 0.22% and 0.33% per transaction, which is actually ~2x the fee of the Visa network (0.13%)! Visa is extremely efficient at moving money anywhere in the world.

Credit and debit card transactions have higher fees because unlike Pix, there is chargeback risk, and the the merchant and acquiring banks party to the transaction are compensated for the risk they assume in those transactions. Pix on the other hand is digital cash. When you spend it, it's gone. Unlike with chargebacks and disputes, there is no reliable mechanism to recover funds for goods not delivered.