Cheap leads, expensive customers
Platforms optimize for whatever you count. Count form fills and you get form fills, many from people who will never pick up the phone.
Join spend to sales
Cost per customer needs one join: ad spend to closed sales, through the CRM. Once it exists, budget decisions get easy and arguments get short.
Feed the signal back
Send qualified and won events back to the ad platforms so their algorithms learn what a customer looks like, not just what a click looks like.