You should pay no more per lead than the sales conversion rate and customer contribution can support. A CPC campaign can produce a low raw cost per lead and still lose money when the forms are unqualified, duplicated or never contacted. Set the target from customer economics, not an industry average.
Calculate the commercial ceiling
Start with the target cost per new customer. Multiply it by the proportion of valid leads that become customers:
Maximum cost per lead = target cost per customer × lead-to-customer rate
If the business can spend £400 to acquire a customer and 20% of valid leads close, the implied ceiling is £80 per valid lead. Build a safety margin below the ceiling to account for uncertainty and operating profit.
Define what counts as a lead
Separate raw submissions, valid contacts, marketing-qualified leads, sales-qualified opportunities and customers. Exclude spam and duplicates from the denominator, but keep them visible as a campaign quality problem. Agree the definition with sales before building a dashboard.
This is where CPA CPC and CPM marketing campaigns need a shared outcome language: channels may buy media differently, but a qualified lead should mean the same thing across them.
Find the hidden cost
Add management, creative, landing-page and sales-handling costs where the decision requires full acquisition economics. Measure contact rate and response time. A lead generated for £50 but ignored for two days may look like an advertising failure when the loss occurs in operations.
Use a range for new campaigns
Estimate low, expected and high close rates. If the target only works in the optimistic case, reduce risk by narrowing intent, improving qualification or testing a smaller segment. Do not lower the target merely because the ad platform recommends one; the business must be able to fulfil it.
Improve quality before volume
Clarify price, location, eligibility and service details in the ad and page. Use relevant search terms, a purposeful form and closed-loop sales feedback. Feed qualified outcomes back into campaign reporting where appropriate.
Our article on lead quality versus click volume explains the measurement trap in more detail. Digital Marketing in Practice teaches paid campaign metrics alongside landing pages, analytics and commercial decision-making.