How CardboardSniper prices every listing
Every alert CardboardSniper sends carries a fair-value claim, so this page spells out exactly where that number comes from and when we refuse to show one.
What is a grade-matched comp?
A grade-matched comp prices a card only against recorded sales of the same card in the same grade from the same grading company. A PSA 8 is judged against PSA 8 sales. A BGS 9.5 against BGS 9.5 sales. Raw cards are judged against raw sales.
This sounds obvious, and almost nobody does it consistently, because thin grades are inconvenient. Crossing grades to fill the gap produces confident numbers that are simply wrong.
The fair value formula
Fair value is the average of the last 3 sane sales for the exact card and grade. Sane means outliers are trimmed first: a sale wildly above or below the recent band, usually a mislabeled variant or a shill result, is excluded before averaging.
Averaging the last 3 keeps the number current without letting one strange sale swing it. Trend direction over the recent window rides along where there are enough sales to compute it.
When we refuse to show a number
If a card has no recent sales in the listed grade, CardboardSniper shows no verdict. No estimate, no interpolation from nearby grades, no model output dressed up as a comp. You still get the alert; you just do not get a number we cannot stand behind.
One misleading verdict costs more trust than a hundred correct ones earn. This rule exists so every number you do see means the same thing.
Where the sales data comes from
Comps draw on recorded sales across major marketplaces and auction results, resolved to the exact card, grader, and grade, including parallel and refractor separation so a base card is never priced against its refractor.
The same pricing engine powers the market pages at gradedworld.com, where you can browse full per-grade sales histories for thousands of cards.
Frequently asked questions
Why average 3 sales instead of using the last one?
A single sale can be an outlier in either direction: an auction that ran hot, a mispriced Buy It Now, a shill bid. Averaging the last 3 sane sales keeps the number current while smoothing one-off noise. It is the same discipline a careful dealer applies by eye.
What counts as an outlier?
Sales far outside the recent band for that card and grade are trimmed before averaging. In practice these are almost always mislabeled variants, damaged-slab discounts, or manipulated results rather than real market moves.
Do you ever mix grades or graders in a comp?
No. Grade-matched means the comp uses only the same card, same grade, same grading company. If that slice has no recent sales, the alert shows no verdict instead of borrowing from a neighbor grade.
Can I see the comps behind an alert?
Every alert shows the fair value, the gap to the listing price, and the grade it was computed for. For deeper history, each card links to full per-grade sales data on gradedworld.com, which runs on the same pricing engine.
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