How Our Values Are Calculated
Every value on StereoWorth is computed algorithmically from real market data. No value on this site is a guess, an appraisal, or an opinion. This page explains exactly where the numbers come from, so you can judge how much weight to give them.
Where the data comes from
Once a day, we query eBay's public Browse API for every model in our catalog and record the current listings. We never scrape eBay pages — all data comes through the official API. Each model has a hand-tuned search query and a list of exclusion terms that filter out the junk that pollutes naive searches: knobs, faceplates, lamp kits, dust covers, service manuals, "for parts" lots misfiled as working units, and accessories that merely mention the model number.
Listing classification
Qualifying listings are sorted into three bands. Restored / serviced means the title or condition indicates professional service, recapping, or restoration. Working is the default band for functional units. Parts / not working covers units sold as-is for repair. Speakers sold as pairs are normalized so values are comparable.
Trimmed medians, not averages
Each band's value is a trimmed median of asking prices: we discard outliers at both extremes before taking the middle value. A median resists the $9,999 fantasy listing and the $50 typo far better than an average. The sample size behind every figure is shown next to it, along with a confidence label — a median of 30 listings means more than a median of 4, and we say so rather than hide it.
Asking prices vs. sold prices
Most values on this site are based on asking prices of active listings, and every such figure is labeled that way. Asking prices typically run above what items actually sell for. Where we show a sold or market value figure, it comes from our own archive: we snapshot every fixed-price listing daily, and when a Buy-It-Now listing disappears before its natural end, we record it as a probable sale at its last asking price. Auction listings are excluded from this inference because they end on a schedule regardless of whether they sell.
Price history
Price-history charts are built from our daily archive. A point is plotted only for days a model was actually re-synced with fresh data — we never fabricate a flat line by carrying stale numbers forward, and days without a fresh sync simply are not plotted. Models that trade too thinly for an honest chart (fewer than three fresh data points across two weeks) show no chart at all.
Thin markets
Some models rarely come up for sale. When a model has no qualifying listings, we say exactly that — the page shows its original MSRP (with an inflation adjustment as a rough anchor) and comparable models that do have live data, not an invented value. An inflation-adjusted MSRP is a reference point, never a market value, and we label it as such.
What can go wrong
We publish these limitations rather than pretend they don't exist. Exclusion filters occasionally miss junk listings or exclude real ones; small samples swing the median; a burst of optimistic sellers can move asking medians without a single actual sale; regional and seasonal variation isn't modeled; and probable-sale detection can't distinguish a sale from a delisting. If you spot a value that looks wrong, email [email protected] — corrections to our matching rules ship in the next daily sync.
Independence
We earn affiliate commissions when you click through to eBay and buy something (see our affiliate disclosure). Commissions are the same regardless of what any listing costs or which model you buy, so there is no incentive to inflate values — and the pipeline that computes values has no knowledge of affiliate links at all.