The cheap CAC trap: why your lowest-cost channel might be losing you money

Every account I take over has one channel everyone loves because its CAC is the lowest on the dashboard. Almost every time, that number is hiding something.

The usual culprits:

• It’s cannibalizing organic or branded search. A cheap “acquisition” from a branded search ad or a retargeting pixel catching someone who was going to buy anyway isn’t new revenue — it’s revenue you already had, now with a line item attached to it.
• It skews toward low-value customers. A channel that’s cheap to acquire on but pulls in customers with a worse lifetime value isn’t efficient, it’s just cheap — and those aren’t the same thing.
• Attribution is doing it favors. Last-click models routinely over-credit the channel closest to the sale, even when an upper-funnel channel actually created the demand.

Before I let a client double down on their “best” channel, I check whether performance holds when I strip out branded and retargeting traffic, and I look at 90-day value, not first-order value. Sometimes the cheap channel really is the best one. Often, it’s just the one getting credit for work another channel already did.

Cheap acquisition and profitable growth aren’t the same claim — treating them as if they are is how good-looking dashboards fund bad decisions.