Why one Google Ads campaign paid $25 a click: the bid strategy with no CPC ceiling

A $400 day on 16 clicks

On June 16, one of four search campaigns on a B2B account — the same account behind the Quality Score audit — posted a $25.00 average CPC: $399.94 spent on 16 clicks, zero conversions. The week before it had run $9–10. The three sibling campaigns didn't budge; one held at $9.84. The keywords hadn't changed. The bid strategy had.

The search terms report showed where it went. A single competitor brand name, redgate, billed $63.73 a click — $127.46 for two clicks — and liquibase took another $107.83 across five. Two terms, $235 of the day.

Whether you can cap CPC depends on the strategy

Three of the four campaigns ran Maximize clicks — TARGET_SPEND in the API — each with a maximum CPC bid limit of $10, $5, and $5. Google's Maximize clicks lets you set one: "setting a maximum CPC bid limit can help you to control costs if you find your CPCs are higher than desired." That limit is the fence.

The fourth campaign ran Maximize conversion value — an auction-time Smart Bidding strategy where "Google sets these bids" for each auction. A standard campaign on it has no maximum-CPC field at all; the system owns every bid. The bid strategy, not the budget, decides whether you can cap a click. When the algorithm wanted $25, nothing in the campaign could say no.

One thing did contain the day: the $200 daily budget, the one cap the bid strategy can't remove. Even that let spend reach $400 — Google delivers up to 2× your daily budget on a busy day — but without it, an uncapped CPC has no other ceiling at all. A budget bounds the day; only the bid strategy bounds the price of a click.

Value bidding with nothing to value

Maximize conversion value optimizes to conversion value — and needs conversions to learn from. This campaign had one primary conversion all month, a contact-form lead on June 2, against $3,263.85 in spend and a 0.31x ROAS. With no leads to chase, it optimized toward the proxy it could find: pricing-page views, counted as secondary conversions and valued $10–100. On June 15–16 those values landed — two $100 Redgate pricing-page views and a $50 release-automation view — and the bidder paid up to buy more of them. It was working exactly as designed, toward a $100 page view instead of a lead.

Two faults compounded: the wrong strategy for the data volume, and no ceiling because that strategy forbids one.

What to do about it

1. Match the strategy to your conversion volume. Value-based Smart Bidding wants steady conversions; Google suggests tracking with values and roughly 3 conversion cycles before trusting it. One conversion a month isn't enough to bid on.
2. If you need a hard CPC cap, use a strategy that has the field. Maximize clicks takes a maximum CPC bid limit; Manual CPC lets you set bids outright. Conversion- and value-based Smart Bidding hand that control to Google.
3. Watch average CPC per campaign, not just spend. This campaign drifted from about $4 a click in early June to $25 by mid-month before anything flagged it; daily spend stayed inside budget the whole time.
4. Keep bid strategy consistent across similar campaigns, so one outlier can't quietly run a different rulebook.

How the fix shipped

The account runs on Adjar: bid strategy is a config field, so the inconsistency read as one campaign's value differing from its three siblings. The repair was a three-line diff:

-bid_strategy = "MAXIMIZE_CONVERSION_VALUE"
+bid_strategy = "TARGET_SPEND"
+max_cpc_ceiling_usd = 10

That puts DB Change Mgmt on the same Maximize clicks plus $10 ceiling as the other three. Clicks bill against a fence again, and "is every campaign capped?" is now a question the config answers on every run, not one someone has to remember to ask.