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.