Cost per lead is the wrong target for most businesses
Cost per lead is the standard target in lead generation, and it quietly instructs the account to buy the cheapest leads available.
Cheap and valuable are not the same thing. In most businesses they are inversely related.
The mechanism
Set a target cost per acquisition and smart bidding does exactly what you asked: it finds conversions at that price. It has no way of knowing that the lead from "emergency boiler repair" is worth thirty times the one from "boiler service cost", because to the algorithm both are one conversion.
So it buys more of the cheap one. Reported performance improves. Revenue does not.
The three fixes, in increasing order of effort
1. Differentiate conversion values. Even rough values are transformative. If you know a quote request converts to a sale 20% of the time at an average value of £2,000, that conversion is worth £400. A brochure download might be worth £15. Send those numbers.
Then switch the strategy from cost-per-acquisition to return on ad spend, and the account starts optimising for money instead of count.
2. Split conversion actions by real intent. A phone call over 90 seconds is a different event from a 20-second one. A quote form is different from a contact form. Once separated, they can carry different values and be included or excluded from bidding independently.
3. Import qualified outcomes. Offline conversion import sends back what actually happened — the lead that became a customer, at what value, weeks later. This closes the loop entirely and is the only version that optimises for the real objective.
Why most accounts stop at step zero
Because values require someone to know them, and that person is usually in a different department from whoever runs the ads.
The conversation worth having is not technical. It is: what is a lead from this form actually worth to you, on average, including the ones that go nowhere? An approximate answer beats no answer by an enormous margin.
The number to watch instead
Revenue per click, or value per click, over cost per click. It is the ratio that decides whether the account makes money, and it is insensitive to conversion volume in the way cost per lead is not.