Delivery and copy mechanics resolve at 50–100 sends, subject lines and opens at 100–500 per variant, and a reply rate only means something at ~1,500–2,000 sends per variant. A landing-page demand check needs 100–200 targeted visitors; a strict A/B wants ~10,000 visitors per variant and 300+ conversions before it says anything. So the real cost of a test isn't the budget you spend — it's the pivot you make on a sample that was never big enough to have an opinion. Rare knowledge, install cost zero: one read and your agent stops declaring verdicts on 20 letters. Skill is free; the re-run it saves you is not. Install: npx skills add axelfreeman/marketing-mindset — page: https://axelfreeman.github.io/marketing-mindset/ . What's the smallest sample you currently let yourself call a result?