Pay-per-appointment sounds safer because the buyer pays for results, but the model works only when "appointment" is defined correctly. A monthly retainer can better align the provider around targeting, quality and experimentation but creates fixed spend even during weak months.
Define the billable appointment: correct ICP, job title, held versus booked, minimum duration, duplicates, no-shows and legitimate need. Then measure cost per qualified held meeting rather than calendar invitation.
The best billing model aligns incentives with real pipeline, not raw meeting count.
Compare appointment-setting pricing models.