It's not the sender, but the receiver. CNPJ's ("SSNs" for Juridic/Business entities) pay a % of the received money.
Many banks, specially the neobanks/fintechs are making it free for small business tho.
I have a business to sign contracts for soft dev and I was charged once for a pix transaction between another business account on a different bank.
That bank is not my primary anymore, I started transferring using the old system (TED) to avoid it. TED takes ~15 minutes (from 0800 to 1700) instead of <1 sec (24h/7d), so not a big loss for internal transfers.
Still using the dumb bank because of other reasons, but not primary.
So competition working as intended in this case.