Revenue ≠ Gross Profit ≠ Net Profit
Seller Central may show strong revenue while the underlying product economics are weak. The first job is to separate top-line sales from the costs required to generate those sales.
Selling Price − Amazon Fees − Product Cost − Prep & Freight − Returns/Refund Impact − Storage/Operational Costs = Contribution Profit
1. Start With the Actual Selling Price
Use the price you realistically expect to collect, not an optimistic target. If the ASIN frequently moves between price points, model a conservative case as well as the current Buy Box price.
2. Include Amazon Fees
Depending on the product and fulfillment method, Amazon charges selling and fulfillment-related fees. Model the current applicable fees for the product rather than using an old spreadsheet assumption. For FBA products, size and weight can materially affect the result.
3. Use Complete Product Cost
COGS should reflect what the inventory actually costs the business. For wholesale this usually starts with the supplier invoice. For imported or private-label inventory, landed cost may also include freight, duties and other costs necessary to bring the product to the point where it can be sold.
4. Add Prep and Inbound Freight
Prep-center fees, labels, polybags, bundling, inspection, cartons and freight into Amazon are often small per unit, but they can erase margin on low-priced products. Allocate them consistently instead of leaving them in a general expense bucket.
5. Model Returns, Refunds and Storage Exposure
Not every unit produces a clean sale. Review historical return/refund behavior where data exists. Also consider whether slow inventory will create storage costs or tie up cash long enough to make the original ROI assumption unrealistic.
6. Separate Advertising From the Product's Base Economics
For brands and private label, advertising can be an important acquisition cost. It is useful to understand the product's economics both before advertising and after expected advertising spend. If the product only works under unrealistically low ad assumptions, the problem may be the unit economics rather than the campaign.
Margin and ROI Answer Different Questions
Contribution Margin tells you what share of sales remains after the modeled variable costs. ROI helps you compare the profit generated with the cash invested in inventory. A product can have an acceptable margin but poor cash efficiency if it turns very slowly.
Illustrative Example
Assume a product sells for $30. After current Amazon fees, product cost, prep and inbound freight, the modeled contribution is $5 per unit. That is an illustrative contribution margin of about 16.7% before any additional business-level overhead. This example is not a fee quote or performance forecast; real inputs must come from the actual product and current Amazon fee structure.
Use the Model Before You Buy
The most useful time to calculate profitability is before the purchase order is placed. Then update the model after inventory is received and again after real sales data exists. The difference between planned and actual economics often reveals freight allocation, fee changes, return behavior or purchase-cost issues.
For a purchase-level review, use the Amazon Profitability Checklist.