18 Mar 2026 · 10 min
Blending CRM revenue with media spend without double-counting
The tempting shortcut is to add platform-reported conversions to CRM new customers and call it coverage. That shortcut invents people. User Acquisition Cost Analytics has to start from customers the warehouse can name.
A marketplace alumni team once showed us a “blended CAC” that looked almost reasonable. They had summed Meta purchases, Google conversions, and CRM first orders, then divided spend by the total. Several thousand people existed twice. A few existed three times. Finance noticed because contribution margin per “new” customer was impossible.
One identity spine
Pick a spine: usually the CRM customer ID, sometimes an order ID if B2C checkout is clean. Media identifiers (click IDs, campaign IDs) attach to that spine. They do not get to create a parallel census of humans. If a click cannot be joined, it remains spend without a named customer — unattributed acquisition cost, not a ghost conversion.
Revenue that is allowed in the numerator
Booked revenue, after discounts, after failed COD, after refunds inside the policy window. Platform “purchase value” is a hint, not a booking. If finance recognises subscription deferral or marketplace commission, your CAC numerator must use the same recognition. Otherwise you are blending two accounting systems and calling it insight.
Double-counting in partnership spend
Affiliates, KOLs, and marketplace ads often invoice on orders that also appear in paid social click paths. Decide once: either partnership spend sits in a separate ledger line, or you allocate with a written rule (first click, last click, or even split). Silent double inclusion is how CAC looks cheaper right before an audit.
What we do in class
In join-key week of the CAC Measurement Studio, students bring an anonymised spend file and a CRM extract. The exercise is not to produce a pretty CAC. It is to count how many orders have a campaign ID, how many do not, and what percentage of spend is therefore “unjoined.” Teams are often shocked. That shock is the beginning of a real number.
If your join rate is low, a Measurement Residency will not magically raise it. An engineer will. We will help you write the question clearly. See pricing or write to the studio.