Cost per lead is the most reported and least useful number in multi-location marketing. It rewards volume, hides quality, and can be improved by making your forms worse. Every operator who has bought aggregator leads knows exactly how that ends.
Cost per booked appointment forces three teams into the same room: the media team that generated the inquiry, the front desk that booked it, and the operator who staffed the hour. When that number moves, something real changed.
Cost per kept appointment is better still. It absorbs no-shows, which are a scheduling and reminder problem that marketing usually declines to own. One network we work with cut no-shows from 21% to 7% and their effective acquisition cost fell by a third without touching media spend.
The instrumentation is not exotic. Tie the inquiry to the booking system, tie the booking to the visit, and accept a two-week lag in reporting. Anyone selling you same-day attribution on a booked appointment is selling you a form fill.
Pick the number, put it on the wall by location, and let it settle the arguments. It will settle most of them.