Separate the visible discount from total promotion cost
The shopper sees the discount, but the seller may also absorb promotion charges, higher advertising spend, and a different fee base. Build the promotional order as its own scenario instead of subtracting the coupon amount from normal profit.
Calculate profit at the redeemed price
- Reduce net sales by the seller-funded discount.
- Recalculate percentage-based marketplace costs using the applicable base.
- Add promotion charges and the expected advertising cost per order.
- Keep fulfillment, product, packaging, and returns costs in the scenario.
Estimate the required incremental volume
Compare contribution profit per promoted order with the normal order. The lost contribution must be recovered through genuinely additional orders, not orders that would have happened at full price. Use a conservative incrementality assumption.
Review after the promotion ends
Measure redeemed units, total units, ad spend, contribution profit, and any post-promotion sales change. Keep the result by SKU and offer type so future promotions start from observed economics rather than a generic discount rule.