Blended CAC vs. Paid CAC
Blended CAC doesn't hide anything wrong. It simply hides whether your growth still depends on an organic channel that will one day stop compensating for the paid channel's inefficiency.
“A healthy Blended CAC hiding a Paid CAC that doubled in a year isn't good news. It's good news with an expiration date.”
Otto GTM ObservatoryWhy the aggregate number hides scalability risk
Blended CAC calculates the average acquisition cost across all channels, including organic ones with low or zero marginal cost (referral, organic, word of mouth). This number can appear stable or improving even when acquisition cost on paid channels is rapidly worsening, simply because the organic channel is absorbing and masking that deterioration in the aggregate average.
Paid CAC, isolated to paid channels only, is the metric that's actually predictive of how scalable future growth is: if a company needs to significantly increase new customer volume, it will almost certainly need to increase paid channel spend, and it's Paid CAC, not Blended CAC, that says how much that additional growth will really cost.
Anti-patterns
Common mistake: presenting only Blended CAC to investors or the board as an acquisition efficiency indicator, without separately showing Paid CAC, which can reveal a much more worrying trend.
Second mistake: planning an aggressive growth plan based on the implicit assumption that the current Blended CAC will stay stable as budget increases, when in reality the spending increase will fall almost entirely on paid channels with a structurally higher CAC.
Practical Application
A company reports a stable Blended CAC of €1,850 for three consecutive quarters, presented as a sign of solid commercial efficiency. Breaking down the figure, Paid CAC went from €2,400 to €4,100 over the same period, compensated only by organic channel growth from 20% to 38% of total acquired customers: a growth plan doubling paid budget would have brought the real Blended CAC to around €3,600, not €1,850.