The floor: what a customer costs

Cost per click divided by conversion rate, for your market, your industry and the specific kind of conversion you are selling — a booking is not a download and a B2B licence is not an impulse purchase. Benchmarks are held at the finest detail available and widened when the data is thin, and the answer says how far it had to widen.

There is a second step most tools skip. What an ad platform can measure is a form filled in or a button clicked; what you actually care about is a customer. The rate between those two is usually offline and almost always ignored, which is how a plan can look comfortable by a factor of ten and be wrong. Jules models it explicitly, and if you do not know it, says so rather than assuming it away.