A one-question survey after checkout - 'how did you hear about us?' - that asks the customer directly what every attribution model tries to infer. The answers are directional, not precise: people misremember, and 'Instagram' might mean an ad, a creator or a friend's post. But the survey is immune to the attribution games platforms play, it captures channels pixels cannot see (word of mouth, podcasts, offline), and it costs nothing to run. The mistake is treating it as too crude to bother with while trusting platform dashboards that over-claim every sale. Crude and honest beats precise and wrong.
Benchmark. Live from day one, for every brand - it delivers 80% of the attribution insight at 0% of the cost. The practical measurement stack is post-purchase surveys plus MER plus nCAC; that is genuinely it until $100K+/month spend.