Amazon sellers often watch revenue first, then profit later. That order is dangerous. Revenue can grow while contribution profit falls because ads, fulfillment, referral fees, returns, and storage costs move faster than sales.
A unit economics model turns each SKU into a decision: scale, reprice, pause ads, renegotiate supply, change fulfillment, or stop buying inventory.
Start with contribution profit
Contribution profit is what remains after the variable costs of one unit. For Amazon, that usually means sale price minus product cost, referral fee, FBA or fulfillment cost, shipping assumptions, ads, coupons, returns, and tax assumptions where relevant.
The goal is not to create an accounting system. The goal is to know whether the next unit sold helps or hurts the business.
Know your break-even price
Break-even price is the lowest price where the SKU covers its variable costs. It is useful before coupons, PPC changes, seasonal promotions, and inventory buys.
If a campaign pushes sales below break-even, the seller may be buying ranking with cash. That can be strategic, but it should be intentional.
Separate ad decisions by SKU
A blended ACOS can hide weak products. A SKU with high margin may tolerate higher ad spend. A low-margin SKU may become unprofitable with the same ACOS.
Track ads by SKU and compare them against contribution profit, not only revenue.
Use the model every month
- Update product cost and fulfillment assumptions.
- Review referral fees, FBA costs, storage and return impact.
- Compare price scenarios before changing discounts.
- Flag SKUs with positive sales but weak contribution.
- Buy inventory only when the model supports the decision.
The best sellers do not just sell more. They know which sales deserve more capital.
Turn marketplace data into pricing decisions
MarketUnit by Tradai sells digital unit economics models for Amazon and Mercado Libre sellers. Use the model before you change prices, scale ads, or buy more inventory.