Cheap leads are easy to buy and easy to waste. The only number that maps to revenue is what a booked, qualified appointment costs you.
A $6 lead that never answers the phone costs infinitely more than a $22 lead that shows up on your calendar. Cost per lead is a media metric. Cost per appointment is a business metric.
Once you switch the target, campaign decisions change. Broad interest audiences that produced volume get cut. Emergency-intent search terms that looked expensive turn out to be the cheapest source of booked work. Creative that filters — price bands, service area, job type stated plainly — starts outperforming creative that maximizes clicks.
Track four numbers weekly: spend, leads, appointments booked, and appointments held. The ratio between the last two exposes reminder and no-show problems that no amount of ad optimization will fix.