A WebFX conversion rate optimization retainer starts at $1,800 a month, according to the agency's own published pricing page. That number shows up on nearly every "CRO pricing" search result. The number that does not show up anywhere near it: how much traffic has to hit the page being tested before that retainer produces a result instead of a stalled dashboard.
Every roundup of conversion rate optimization pricing ranks retainers, project fees, and hourly rates against each other, then moves on to a "which agency is right for you" section. None of them ask the question that actually determines whether the price is reasonable: does this site send enough visitors to the page in question to finish a test before the contract renews twice. Our analytics team gets pulled into CRO conversations more often to answer that traffic question than to argue about which agency's rate card is fairest.
TL;DR:
- A full-service CRO retainer starts around $1,800 a month at the lower end, per WebFX's own pricing page.
- A/B testing vendor Convert Experiences publishes a working benchmark of about 10,000 visitors and 1,000 conversions per variant before a test is conclusive.
- Below that traffic level, a retainer bills every month while the test is still collecting data, not producing wins.
- The traffic a page already gets, not the agency's rate, is the number that should decide whether to sign a CRO contract now or fix something cheaper first.
What a CRO retainer is actually buying
"Conversion rate optimization" covers a specific bundle of work, not a single tool. A retainer typically includes user journey analysis (mapping where visitors drop off before converting), A/B or multivariate testing (running two or more versions of a page against each other), heatmap and session recording analysis (seeing where people click, scroll, and hesitate), and conversion funnel optimization (fixing the specific step losing the most people).
Most of the tools behind that work, heatmap software, testing platforms, session replay, are commodity software at this point. What an agency retainer is really selling is the analyst time to read that data correctly and the testing discipline to run experiments that produce a real answer instead of a coin flip dressed up as insight.
The real starting price
WebFX's own CRO pricing page lists plans starting at $1,800 a month, including A/B testing, 40-plus report and action-item options, and a dedicated team of UX specialists. That is one named agency's actual published floor, not a market-wide average, since most CRO agencies quote custom pricing after a discovery call rather than publishing a rate card at all.
What that number does not include is any guarantee about how fast a test resolves. A $1,800 monthly retainer on a page that gets heavy traffic can produce a winning variant inside a few weeks. The same retainer on a page that barely gets visited can run for most of a year without a single statistically valid result, and the invoice does not change either way.
The traffic math nobody puts on the pricing page
Convert Experiences, an A/B testing vendor, publishes a working rule of thumb: send roughly 10,000 visitors to each variant and collect around 1,000 conversions per variant before treating a result as conclusive. That is the vendor's own stated benchmark for its own product category, not a number borrowed from a blog roundup.
As an illustration, a landing page getting 2,000 visits a month, split evenly across a control and one variant, would take roughly ten months just to accumulate 10,000 visits per variant, before even counting how long it takes to also reach 1,000 conversions on each side. A retainer signed against that page is paying for ten-plus months of data collection before the agency can tell you anything with confidence.
Optimizely's own sample size documentation confirms the same underlying mechanic from a different testing platform: the sample size a test needs is a function of the page's existing baseline conversion rate and how small a lift you want to be able to detect, with 95% statistical significance treated as the accepted standard. A lower baseline conversion rate or a smaller lift you're trying to catch both push the required sample size, and therefore the required traffic and time, higher. Neither vendor's documentation mentions price. Both describe the same traffic floor a retainer has to clear to be worth paying for.
What to check before signing a CRO contract
The traffic number that matters is not total site traffic, it is traffic to the specific page or flow being tested. As an illustration, a site with 50,000 monthly visitors spread across 200 blog posts can still have a checkout page that only sees 1,500 visits a month, and that checkout page is the one a CRO retainer would actually be testing.
Before signing anything, pull the monthly visitor count for the exact page in question from whatever analytics tool is already in place. If that number clears something in the range of the 10,000-per-variant benchmark within a month or two, a retainer has a real shot at producing results on a normal contract timeline. If it does not, either pick a higher-traffic page to test first, or spend a few months on cheaper traffic-growth work before paying for optimization on traffic that does not exist yet.
It also helps to ask the agency directly what happens if a test does not reach significance inside the contract term. Some retainers roll an inconclusive test into the next month at no extra charge and simply keep collecting data. Others treat each test as a billed deliverable regardless of outcome, which means a low-traffic page can generate several "completed" invoices without ever producing a result worth acting on. That distinction matters more than the headline monthly rate, since it decides who absorbs the cost of a traffic problem that CRO itself cannot fix.
Once a test does produce a winning variant, the next question is usually how fast that win gets rolled out everywhere it should apply, into email flows, onboarding sequences, or CRM follow-up logic, instead of sitting as a one-off page edit. That handoff is where our workflow automation team typically gets looped in, wiring a confirmed winning variant into the systems that already run follow-up and lifecycle messaging so the lift shows up everywhere the page's logic is reused, not just on the one URL that got tested.
Whether this is worth paying for right now
A CRO retainer is a bet that the traffic already exists to make testing fast. On a page that clears the volume a testing vendor itself says it needs, that bet usually pays off inside a normal contract term. On a page that does not clear it, the retainer is really just paying rent on a dashboard that is still waiting for enough visitors to say anything.
Tell our analytics team how much traffic your highest-intent page actually gets, and we'll tell you honestly whether a conversion rate optimization program is ready to pay for itself yet, or whether the traffic and tracking work has to come first.
