A blended acquisition cost is an average of things that behave nothing alike. Brand search, retargeting and cold prospecting all land in the same number, and the healthy channels quietly subsidise the broken one for months before anyone notices.

Start by splitting demand capture from demand creation

Brand search and retargeting capture demand that already exists. Cold prospecting and most content work create it. Averaging the two produces a figure that is stable, comforting and almost entirely useless for deciding where the next thousand should go.

The cheapest diagnostic available

Turn one channel off for two weeks and watch what happens to total revenue, not to that channel’s reported conversions. If nothing moves, you were paying for demand you already had. This is uncomfortable, cheap and more honest than any model.

What to report instead

• Cost per qualified lead, per channel, with the qualification rule written down.
• A holdout-validated incrementality figure for your largest paid channel.
• New-customer acquisition cost separated from total acquisition cost.

None of this requires a warehouse. It requires agreeing, once, what counts as qualified — and then not quietly changing the definition when the number looks bad.