A promotion can increase conversion while reducing revenue per order and contribution. It may also shift purchases forward in time, reward customers who would have paid full price, or attract one-time deal seekers. A campaign’s higher conversion rate is not proof that the offer created profitable demand.
Calculate CAC with clear customer rules
For new-customer CAC, divide the relevant acquisition spend by first-time customers acquired in the same period or properly attributed cohort. Keep new and returning customers separate. If spend and acquisition lag materially, use cohort-based matching rather than dividing unrelated calendar totals.
Measure the true cost of an offer
Track discount dollars, net sales, refunds, product cost, fulfillment, payment fees, and variable marketing. Compare contribution per order and per acquired customer, not only gross revenue. Include the cost of discount codes funded by the brand and distinguish them from retailer-funded promotions.
Test incremental lift, not coupon redemption
Compare eligible customers or geographies exposed to the offer with a valid holdout. Check whether the offer creates additional orders or merely subsidizes existing demand. Monitor full-price purchases after the promotion to identify pull-forward effects.
Make attribution promotion-aware
Tag campaigns and offers consistently, and segment performance by discount depth and first-order promotion. ThoughtMetric may help examine channel paths and campaign context, but reconcile attributed sales to actual order-level discounts and test whether promotions generated incremental contribution.
At a glance
| View | What it includes | Why it matters |
|---|---|---|
| Platform ROAS | Platform-attributed revenue ÷ ad spend | Campaign optimization signal |
| Revenue CAC | Ad spend ÷ new customers | Acquisition volume efficiency |
| Contribution CAC | Acquisition spend relative to contribution generated by new customers | Economic quality after variable costs |
| Offer incrementality | Difference between test and holdout outcomes | Whether discount caused additional profitable demand |
Frequently asked questions
Should discounts be included in CAC?
Discounts are not usually part of media CAC, but they should be included in acquisition economics and contribution analysis because they reduce realized revenue.
Can a coupon campaign have high ROAS but lose money?
Yes. Attributed revenue may look strong while discounts, product costs, returns, and fulfillment leave little or negative contribution.
How do I know if a promotion attracts low-value customers?
Compare mature cohorts by offer exposure, repeat purchase, net revenue, and contribution profit. Control for channel, product, season, and customer mix.
Should I stop all first-order discounts?
No. Test offer types and thresholds. A smaller incentive, bundle, free shipping, or value-added offer may create better contribution than a deep percentage discount.
The most reliable measurement system combines consistent definitions, reconciled commerce data, channel diagnostics, and experiments. Review assumptions whenever your store, tracking setup, or marketing mix changes.
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