Sold-comps stats on eBay search pages

The idea

A reseller standing in a Goodwill aisle holding a jacket makes a buy decision in thirty seconds: search eBay, tap the sold filter, and squint at a wall of listings trying to mentally average prices and judge whether the thing actually sells or just gets listed. That eyeballed maths decides hundreds of dollars of buys a week, and the number that matters most, sell-through rate, is not shown anywhere on the page.

eBay’s own Terapeak has this data, buried inside Seller Hub where nobody opens it mid-sourcing. The wedge is zero clicks: stats appear on the sold-search page the reseller is already looking at, on the phone-sized decision timeline they actually operate on. Computing sell-through from sold-versus-active counts is the differentiator, since price averages alone are easy to eyeball.

Who pays

The reseller pays $8/month, judged against buy decisions where one avoided dead-stock purchase covers a year. Buyers are the same audience as every reseller tool: r/Flipping, reseller YouTube and its sponsorship economy, and BOLO (be on the lookout) Facebook groups. The extension demos perfectly in a 30-second video, which is exactly the content this niche consumes.

MVP scope

• Stats bar injected on eBay sold-search results: average, median, range, sold count
• Sell-through rate from a background fetch of the active-listing count, with traffic-light colouring
• Outlier stripping and auction-exclusion toggles, live recompute on scroll
• Save-comp snapshots with a popup list and CSV export
• Skip for v1: eBay API integration, historical trend charts, mobile support, other marketplaces (Poshmark, Mercari), and listing-creation features

Build CompStat, a Chrome extension that overlays pricing statistics on eBay sold-listing searches. Stack: Plasmo framework, Chrome extension APIs (content scripts, chrome.storage.local), Stripe for the licence.

Core flow: a content script detects when an eBay search has the Sold Items filter active, parses the visible results (title, sold price, sold date, shipping where shown), and injects a stats bar pinned above the results: average price, median price, price range, sold count, and sell-through rate. Sell-through is the decision-making number: compute it by fetching the same query without the sold filter in the background (one fetch of the active-listings count from eBay's own results page), then sold divided by (sold + active), displayed as a percentage with a traffic-light colour (green above 70%, amber 40-70%, red below).

Handle the messy realities: strip outliers beyond 2.5 median absolute deviations with a toggle to include them, exclude auction listings with heavy bidding noise via a checkbox, and recompute stats live when eBay's infinite scroll or pagination loads more results.

Add a Save Comp button that snapshots the query, stats, and date into chrome.storage.local; a popup lists saved comps so a reseller sourcing on Saturday can price their listings on Sunday. Include CSV export of saved comps.

Settings page: outlier toggle, currency, licence key. Monetisation: 14-day trial, then $8/month via Stripe payment link with licence-key validation.