email-lifecycle-offer-math

1# offer-math
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3**Reads:** `../email-lifecycle/references/segments-cadence-offers.md` (ladder and formula); AOV and margin per product or category from `lifecycle/program.md` (marketer-stated); the standing first-order offer from the shared `Standing offer:` fact (else the Brand record's business facts, read with `file_read`; never a search snippet); product records for price.
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5**Does:**
61. **Check the offer is allowed:** the standing offer, or a step of a ladder the marketer approved. Welcome never deeper than the standing offer; first cart reminder never discounted; no discount to returning full-price buyers in cart flows; no code twice in 30 days. Anything else is a proposal, not a draft.
72. **Compute** contribution per order, discount cost per order, share of contribution used, and the break-even lift, with the inputs shown. Free shipping: cost = average shipping cost × share of orders newly qualifying. Rewards (referral): cost per successful referral both sides vs contribution of the referred first order. Subscriptions and apps: use the subscription formula in the reference (store fee, months retained).
83. **Leakage:** shared vs unique code (if the sign-up form shows a shared code, repeat that code and flag the leakage as a proposal naming the popup edit — never switch it silently), stacking, exclusions, expiry, which segments see it (are full-price buyers in them?).
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