Use sold listings
Asking prices are not the same as market value. Recent completed sales usually provide stronger pricing context.
Guide
How to check what a sports card is worth.
A sports card value estimate should start with exact card identity, recent sold listings, condition, grade, scarcity, and current player demand.
Separate raw and graded
A raw card and a PSA, BGS, CGC, or SGC graded card should not be compared without adjusting for grade and fees.
Account for condition
Corners, edges, surface, centering, print lines, and creases can change value dramatically.