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Methodology · 4 min read · June 18, 2026

How Graded Card Values Are Determined (Real Comps Explained)

There is no official "price" for a graded card — only what comparable copies have recently sold for. Good valuation is the disciplined version of that idea. Here is how Slabline does it, and how to read a value with confidence.

Comparable sales, not list prices

A value is built from recent sales of the exact same card and grade — same year, set, player, number, grader, and grade. Asking prices and outliers are noise; realized sales are signal. Slabline aggregates comps across eBay, Heritage, Goldin, and PWCC.

More sales, tighter value

A card that trades often (high sales volume) produces a confident, narrow value. A card that rarely sells has a wider range — one outlier sale can swing it. That is why Slabline shows sales volume alongside the value: it tells you how much to trust the number.

Why it stays current

Markets move fast in the hobby. A value from last season can be badly stale. Slabline re-pulls comps continuously, so your collection total — and your insurance schedule — reflect today, not a snapshot from a year ago.

Know what your collection is worth — and how well you’re protecting it.

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