Cost per lead is what it costs you to get one contact: ad spend divided by number of leads. If you spend €500 and get 100 contacts, your cost per lead is €5. Simple to calculate, easy to misread.
The misreading is thinking 'low' is always better. A €0.50 cost per lead is great if those leads book and buy, and terrible if they're cold contacts who never answer. The number is never read alone: read it together with lead quality and how well it converts into a call and a client.
What lowers cost per lead: a low-barrier entry offer, a quiz or a guide, instead of the blunt consultation request; an ad that matches the page; a well-chosen audience. What raises it: sending traffic to the home page, asking too much too soon, broad generic targeting.
Some real costs from my accounts, so you have a yardstick. An ebook funnel in the legal niche: €1.30 per contact. A public-procurement firm (Spatara): €1.34. A debt and business-crisis practice (Volpe): €2.30. The AsteNow quiz in real estate: €0.90 per lead. These are lifetime Ads Manager figures, not estimates.
Why do they vary so much? Because cost per lead depends on the niche, the temperature of the audience, and the barrier of the offer. A free quiz costs less than a consultation request, because it asks for less. Comparing your cost per lead with a different sector's makes no sense: compare it with your own history and with what a client is worth to you.
The right question isn't 'what's a good cost per lead', it's 'how much can I afford to pay'. If a client is worth €3,000 to you and you close one in twenty leads, you can pay far more per lead than you'd think. Cost per lead only makes sense inside your funnel's economics, from contact to revenue.
If you don't have these numbers in front of you yet, it's because the measurement layer is missing. The free 2-minute audit on this site tells you whether that's your engine's weak part or another one.