Lookalike audiences are supposed to be dead — killed by broad targeting and Advantage+. So it surprised us to find a nine-figure beauty brand still deploying them at scale, profitably, except for one campaign group bleeding roughly $50K a month.
The diagnosis
The bleeding campaigns seeded their lookalikes from all purchasers. But 34% of this brand's buyers only ever purchased with a 25%+ discount code — a cohort with near-zero full-price repeat rate. The lookalike dutifully found more of them. The campaigns then acquired discount-hunters at full CAC, who churned immediately.
The fix
Re-seed from full-price purchasers with 2+ orders — a smaller, higher-signal audience of 91K contacts. Within five weeks: CAC down 31% on the affected campaigns, 60-day repeat rate up 2.2×. Total engineering effort: one SQL query and a scheduled audience sync.
The moral isn't about lookalikes. It's that every algorithmic product is a mirror of the data you hand it. The brands winning in 2026 are the ones treating audience curation as seriously as creative.