Target CPA is an average, not a ceiling
People set a target CPA believing it caps the cost of each lead. It does not. Google describes it as an average target: individual conversions may cost more or less.
That statement does not mean Google deliberately buys a bucket of "junk" to subsidise a good lead, and it does not set a click-price ceiling. Smart Bidding sets auction-time bids from its prediction of the selected conversion goal. If every form, call and chat counts equally in that goal, then a wrong number or existing-customer call that meets the configured threshold can be presented to the bidder as the same success as a new customer.
The defensible conclusion is about the signal, not the price of the click. A stable reported CPA can hide a changing mix of business outcomes when the platform conversion definition is too broad. Rising CPCs do not by themselves prove that cheaper or worse traffic is being purchased.
What this looks like in an account
The reported CPA is on target. Conversions are steady. The owner says the phone rings less with real jobs. The search terms report shows the best query losing volume faster than the account overall while the worst query holds up. Job numbers in the CRM are flat or falling while the ads report nothing wrong.
In one trades account we reviewed, total clicks were down 20 per cent, a historically strong term was down 31 per cent and a weaker term was down 19 per cent. That pattern prompted an investigation of goal quality and search-term mix. The figures alone do not prove why the auction system moved.
What to do
First fix the conversion definition. Import eligible CRM outcomes, separate reporting-only actions from primary bidding goals, and assign evidence-based values where outcomes differ. A duration threshold can filter very short calls, but it is not a quality label. Value bidding is useful only when the values are real enough to steer on. If the business objective is maximum output from a genuinely fixed budget, testing a strategy without a target is one documented option, not a universal prescription.