The Math
For investors who trade more than a few times per month, the PFOF execution quality degradation exceeds traditional commission costs. For very infrequent traders, PFOF costs may be lower in absolute terms — but the conflict of interest remains regardless.
Fidelity Proof
Fidelity offers zero commissions without PFOF for equity orders — proving the zero-commission model does not require PFOF. Fidelity simply earns revenue from other sources.