Why cost per signup is the only creator metric that matters

Open any creator campaign report from a typical agency and you'll see the same numbers: impressions, reach, views, engagement rate, maybe a few thousand likes. It looks like progress. It feels like the campaign worked. And it tells you almost nothing about whether the money you spent turned into customers.

For SaaS and AI brands, there is only one metric that actually matters when it comes to creator marketing: cost per signup. Everything else is a proxy at best and a distraction at worst.

The problem with vanity metrics

Views measure attention, not intent. A video can rack up half a million views and drive zero signups if the audience is wrong, the hook is off, or the call to action is weak. Engagement rate measures how much people liked the content — not whether it made them act. These metrics are seductive because they're big, they're easy to report, and they make everyone feel good. But they don't connect to revenue.

The reason agencies lean on them is simple: they're accountable to activity, not outcomes. Reporting on reach lets an agency show effort without committing to results. The moment you shift the conversation to cost per signup, that comfort disappears — and that's exactly why it should be the number every brand insists on.

What cost per signup actually tells you

Cost per signup ties every pound of creator spend directly to a business outcome. It answers the only question that really matters: for every X we spend, how many new users do we get, and what does each one cost us to acquire?

Once you have that number, everything else becomes clear. You can compare creator marketing directly against paid search and paid social. You can model the return based on your free-to-paid conversion rate and average customer lifetime value. You can identify which individual creators are driving conversions and which are just driving views. And you can optimise every month toward a lower cost per signup rather than a higher view count.

How to track it properly

The mechanics matter. To measure cost per signup at the creator level, every creator needs their own unique tracked link — a UTM parameter that identifies exactly which creator drove each click and each conversion. Without creator-level tracking, you're flying blind: you might know the campaign drove 300 signups, but you won't know that 250 of them came from one creator and the other four contributed almost nothing.

That granularity is what makes optimisation possible. When you know which creators convert, you can brief them again, give them more budget, and cut the ones who don't. The campaign gets smarter as it progresses — but only if you're measuring the right thing from day one.

The bottom line

If your creator marketing is being measured in views and engagement, you don't actually know whether it's working. Insist on cost per signup. Track it at the creator level. Optimise toward it every month. It's the difference between a campaign that feels good and a channel that grows your business.