Comping is a browser extension for resellers doing online arbitrage. It shows eBay sold prices and an estimated profit margin for whatever you're looking at, so you can tell in seconds whether an item is worth flipping.
Comping detects product pages using the page's own structured data (the same data Google uses for search results), plus a dedicated detector for Amazon.
Click the small badge that appears to see the eBay sold-price median, range, and a profit estimate compared to the page's price — after eBay's fees and shipping.
No product data on the page? Highlight any text, right-click, and choose "Check eBay sold prices" — or use the toolbar search box.
Checks the eBay site matching the page's currency (US, UK, Australia, Canada, Germany), so the profit math never mixes currencies.
Never appears on search results, carts, checkout pages, or sites without a clear single product — only real product pages. Per-site opt-out if you don't want it on a given store.
Everything Comping stores lives only in your own browser. Read the full privacy policy.