Methodology
How SellerEconomics models profit, fees, margin and break-even pricing.
Core profit model
The core model starts with selling price, then subtracts product cost, shipping cost, advertising cost and marketplace fees where relevant.
The result is net profit per order. Margin is net profit divided by selling price. ROI is net profit divided by seller-controlled costs.
Fee scenarios
Fee schedules are stored separately from the calculator UI. Each production fee rule should include source, effective date, last reviewed date and notes for ambiguity.
When a marketplace fee depends on category or fulfilment details, the calculator should name the scenario rather than present it as universal.
Break-even logic
For simple calculators, break-even starts from seller-controlled costs. For marketplace calculators, the engine solves for the sale price that covers costs and applicable fee rules.
Threshold and minimum fees are modelled explicitly where the source-backed scenario requires them.
Data freshness
Fee profiles show whether they are verified scenarios or still need category selection.
The fee source log should be reviewed before production launch and after any marketplace fee announcement.