Amazon (Keepa API)
Primary pricing source. Keepa provides: current price, 30/90-day average, price range (highest/lowest), sales rank, FBA fee estimates. 1 request per scan, cached 5 min.
eBay API (Finding + Browse)
Search for completed listings to get sold price (more accurate than current asking price). Returns: sold price range, average sold price, number sold in last 30 days.
Poshmark / FB Marketplace
Poshmark API for listing prices. Facebook Marketplace requires scraping (legal gray area — use public data only). These show asking prices, not sold, so note in UI.
FBA Fee Calculator
Use Amazon's official Fee Preview API or calculate locally: fulfillment fee ($3.22–$7.40 per item by size), storage fee ($0.75–$2.40/cubic ft), closing fees. Accurate numbers are critical for trust.