Margin
Profit expressed as a percentage of sale price — the most-quoted profitability metric, often misused.
Margin is profit divided by sale price, expressed as a percentage. There are several variants depending on what costs you subtract first: gross margin (price minus COGS minus Amazon fees), contribution margin (gross minus direct variable costs like PPC), and net margin (contribution minus allocated overhead).
In casual seller conversation "margin" usually means gross margin. The trap: a 35% gross margin on a SKU with 25% TACoS leaves you with only 10 percentage points of contribution margin, before accounting for software, prep, and overhead. Sellers who optimize against gross margin alone often discover their net margin is negative when they finally do a full P&L.
Margin should always be paired with another anchor metric — usually ROI for arbitrage sellers, contribution margin for wholesale sellers, and TACoS-adjusted net margin for private label brands. Don't pick a SKU based on margin alone.