The estimates vary from one study to the next, but they converge on the same uncomfortable order of magnitude: an average Google Ads account is thought to waste between 20% and 40% of its budget on clicks that have no chance of turning into a customer. Before blaming the platform or its bidding, it’s worth looking at what that figure says about our own practices. Because waste, in PPC, is almost never accidental: it’s the direct consequence of a way of measuring that stops too soon.
PPC—pay-per-click advertising, on search engines as much as on social networks—has a rare quality: everything in it is measurable, in real time. That is precisely what makes it dangerous. When everything is measurable, you end up optimizing what is easiest to measure rather than what matters most. The click measures itself in one figure, while return on investment is far harder to pin down.
The Click Is Not the Result
A high click-through rate is pleasant to look at. It says nothing, however, about profitability. An ad can draw thousands of clicks and generate no sales at all—either because it attracts the wrong people, or because what they find after the click doesn’t hold the promise the ad made. The click is a cost you incur well before any result, which comes later: a quote request, a purchase, a qualified lead.
This confusion explains a good share of the waste mentioned above. You steer the campaign by cost per click because it sits at the top of the dashboard, when the only indicator that decides profitability is the cost of acquiring a customer—how much it costs, all in, to land a paying customer. A ten-cent click that never converts is infinitely more expensive than a three-euro click that brings in a contract.
Three Leaks That Eat the Budget
Audits of advertising accounts surface, with an almost tedious regularity, the same three sources of waste. None of them is sophisticated; all of them are costly.
Targeting That’s Too Broad
Running your ads on queries vaguely related to your offer amounts to paying for the attention of people who weren’t looking for what you sell. It’s the most common leak, and the simplest to plug: a list of keywords to exclude, kept up to date from the actual searches that triggered the ads, is often enough to recover a substantial share of the budget. You still have to go and look at those queries—which many advertisers never do.
The Landing Page That Betrays the Ad
An ad promises something; the page it sends people to has to deliver it, immediately. When the click leads to a generic homepage rather than a page dedicated to the offer advertised, the visitor ends up hunting for what they came for—and leaves. You’ve paid for the click, lost the conversion, and degraded along the way the quality score that sets the price of the next clicks. Consistency between the ad and its destination is no mere matter of usability: it works as a direct lever of profitability.
Blind Measurement
You can’t optimize what you don’t measure. A surprising number of campaigns run without conversion tracking properly installed: you know how many clicks you paid for, not how many customers they brought in. As long as that link is missing, any « optimization » happens blind, on surface indicators. Wiring up conversion measurement isn’t one technical formality among others—it’s what lets you steer a campaign at all, instead of flying blind on the numbers it happens to surface.
Measuring the Right ROI: Beyond Cost per Click
Setting a return-on-investment target means tracing the chain back to the real value of a customer. Two indicators serve better than cost per click for that. ROAS (return on ad spend) measures revenue generated against money spent: a ROAS of 4 means four euros earned for every euro invested. Cost per acquisition relates the spend to the number of customers obtained. Both say what the click-through rate will always leave unsaid.
One variable remains that poorly steered campaigns ignore: a customer’s value isn’t limited to their first purchase. If an acquired customer brings in revenue over two years, the tolerable cost of acquisition isn’t the same as if they buy once and disappear. Building that value over time into the equation radically changes a campaign’s break-even point—and sometimes allows you to pay far more for a click than it appears to be worth, because you know what it returns in the end.
The Last-Click Myth
A subtler distortion skews the ROI calculation: most tools credit the conversion by default to the last click before the purchase. Convenient, but misleading. A customer has rarely bought because they clicked once on an ad; they saw some content, received an email, compared, then clicked on a final ad that scooped up all the credit. Steering by last click leads you to cut the campaigns that set the decision in motion—the ones that build awareness—in favor of only the campaigns that close it. You then optimize the end of the journey by sabotaging its start.
You don’t need to build a sophisticated attribution model to guard against this. It’s enough to keep in mind that a campaign’s numbers never tell the whole story of a sale, and to resist the temptation to judge each budget line in isolation. A campaign that’s « unprofitable » on last click can be indispensable to the whole—exactly as you don’t judge a shop window’s usefulness by the sole number of sales closed in front of it.
It’s also at this scale that you compare channels honestly. PPC buys immediate visibility, where organic search builds it slowly but isn’t paid by the click, and where email marketing delivers, on an audience you’ve already won, a return that paid advertising rarely matches. The right budget trade-off rarely comes down to picking one channel over the others; it comes down to knowing what each one really costs per customer obtained.
Going Further
PPC behaves like whatever you choose to measure it by: it’s a channel that returns exactly what you ask it to measure. Ask it for clicks and it will flatter your dashboards while draining the budget. Ask it for value, by tracking cost of acquisition, ROAS and profitability over the customer’s lifetime, and it becomes one of the most steerable levers you have. For an overview of paid advertising channels, our guide to online advertising usefully complements this ROI-focused reading.
If your campaigns are running without your being able to say what a customer really costs you to acquire, that’s probably where your margin is hiding. We can look at your numbers together.
