Mercari Japan Underpriced Deals — Under the Sold Price

What it does: Works out what your keyword usually sells for on Mercari Japan (median of sold listings), then returns the live listings priced below your threshold.

You enter: keywords, e.g. Nikon Z6 (a min price like ¥50,000 keeps accessories out); threshold, default 80%

You get: each deal: price, discount vs the sold median, condition, URL. Per keyword: sold median and range, the sold listings it rests on, live listings checked, deal count and deal rate, biggest deal. Built from the first 120 sold and 120 live listings.

Price: $0.02 per keyword scanned + $0.002 per deal found (deals on by default). Too few or too mixed sold prices = the keyword is refused and not charged. A usable keyword still costs $0.02 when it finds no deals.

Example: enter Nikon Z6 with a ¥50,000 floor → sold median ¥141,995 · 25 deals among the 60 live listings checked · biggest 63.9% off — a run sampled at 60 sold and 60 live, not the default 120 (real run, 2026-08-09)

Unofficial — not affiliated with Mercari. Reads public pages only.

How the score is built

1. Read the sold (sold_out) listings for the keyword → the basis: the median sold price and the middle 50% range around it.
2. Read the live (on_sale) listings.
3. discountPct = (1 - price / soldMedian) x 100 for each live listing.
4. Return every live listing at or below your threshold, plus the price spread on both sides.

Two guards, because a basis can lie in two ways

Too few sold prices. A median built on three sold listings is noise, and a "70% discount" against noise is a bad trade. minComps (default 8) refuses to score such a keyword. When nothing at all sold under the keyword, basisUnusableReason says that instead of calling the market thin — an empty result is a spelling question, and it points you at the Japanese name or another way of writing the model number.

Too many kinds of thing. This one we found by running it (measured 2026-08-10). Search Mercari for Nikon Z6 and you get the camera and its batteries, cases and manuals: sold prices from ¥375 to ¥150,000, median ¥7,240 — an accessory median. Scored against that, a ¥490 product catalogue booklet came back as the best deal at "93.2% off". Arithmetically perfect, completely fabricated.

So the basis must also be coherent. maxCompSpread (default 4.0) measures how wide the middle 50% of the sold prices is (top divided by bottom); a keyword that mixes price tiers is refused, with that number quoted and a pointer to the fix:

{ "keywords": ["Nikon Z6"], "priceMinJpy": 50000 }

priceMinJpy / priceMaxJpy bound both sides of the comparison, so the camera is scored against camera prices. The input form is pre-filled with a ¥50,000 floor for that reason: measured 2026-08-18, Nikon Z6 on its own is refused (13.9x spread) while the same keyword with the floor spans 1.66x and finds 37 deals in 120 live listings. Clear the floor when your keyword is a cheaper product.

In both cases the Actor returns basisUsable: false with basisUnusableReason, and is not charged. The basis is always reported next to the deals (soldMedianJpy, soldCompCount, compSpread, and the full price spread) so you can see what the discount was measured against.

Output

Per keyword, one deal_summary:

field	meaning
soldMedianJpy, soldPriceJpy	the basis, and the sold prices it came from (lowest, middle 50%, highest, average)
basisUsable / basisUnusableReason	whether the basis held, and why not
compSpread	how wide the middle 50% of the sold prices is — how mixed the keyword is
soldCompCount / liveListingCount	sample sizes on both sides
dealCount	live listings at or below the threshold
dealRatePct	share of the live book that is underpriced
discountPctStats	how big the discounts are across the deals (lowest, middle 50%, highest, average)
bestDeal	the single largest discount, with its URL
mixedKeywordLikely	true when an unusually large share of the live listings sit under the median — a sign the keyword still mixes different products

Plus, optionally, each deal as its own record.

Measured on 2026-08-09 (real run) — Nikon Z6 with a ¥50,000 floor, trimmed to the fields above:

{
  "type": "deal_summary",
  "keyword": "Nikon Z6",
  "basisUsable": true,
  "compSpread": 1.46,
  "soldCompCount": 60,
  "soldListingsFound": 446,
  "soldMedianJpy": 141995,
  "soldPriceJpy": { "min": 58000, "p25": 109500, "median": 141995, "p75": 160000, "max": 290000, "average": 152333 },
  "liveListingCount": 60,
  "liveListingsFound": 141,
  "dealThresholdPct": 80,
  "dealCount": 25,
  "dealRatePct": 41.7,
  "mixedKeywordLikely": true,
  "bestDeal": { "priceJpy": 51300, "discountPct": 63.9, "url": "https://jp.mercari.com/item/m79348511603" },
  "checkedAt": "2026-08-09T17:31:59+00:00"
}

(That run sampled 60 sold and 60 live listings; the current defaults are 120 of each.)

Pricing

$0.02 per keyword scanned, plus $0.002 per deal found (individual deals are on by default; turn off Include individual deals to pay the $0.02 only). A keyword with an unusable basis is never charged. A usable keyword still costs $0.02 when it finds no deals. You pay per keyword; there is no monthly fee.

Public data only, no login, requests spaced out. Nothing is stored between runs.

If something goes wrong

• Wrong number or a failed run? Open a ticket on the Issues tab. I read every one and reply within 2 business days (Japan time).
• You never get a fake "empty" result. If the site can't be read, the run fails and says so.
• A keyword that can't be measured = no charge. Too few or too mixed sold prices and the keyword costs nothing. A keyword that could be measured costs $0.02 even when nothing is underpriced right now — that is the answer you asked for.
• Checked every week. An automatic test runs this tool weekly; if the site changes, I fix it.
• Public pages only. No login, no personal data, and it goes easy on the site.

More tools by the same author

• Mercari Japan Sold Prices — What Items Really Sell For
• Mercari Japan Listings — One Row per Item, $0.0015 Each
• Yahoo! Auctions Japan Sold Prices — Median, Range, Bids
• Japan Used Camera & Lens — Dealer Price vs Sold Price
• Japan Figure & Gunpla — New Price vs Used Sold Price
• Used iPhone & Android Prices Japan — Dealer vs Sold
• Yahoo, Mercari & PayPay Japan — Same Item, 3 Prices
• Mercari & Yahoo Japan Demand — Sold vs Still Listed

All tools (Japan marketplaces, real estate, jobs, racing, prediction markets): https://apify.com/jpmarketdata

Disclaimer

Unofficial, independent tool — not affiliated with, endorsed by, or sponsored by Mercari. Product names and logos belong to their owners and only say where the data comes from. Data is read from public pages, for market research; check before you act on it.