The 1987 Topps Mark McGwire #366 is valued at $1.67 raw, $20.03 in PSA 9, $234 in PSA 10 as of November 3, 2026. Its market value is down 10.2% over the last 30 days, from $1.86 to $1.67. Across the 89 days we have tracked it, it has ranged from $1.25 to $2.06, and it currently sits 19% below that high. With 2,325 recorded sales, it ranks in the top 10% of baseball cards we track by trading volume.
On current values, a PSA 9 ($20.03) is worth $6.64 less than a raw copy plus a $25.00 grading fee, while a PSA 10 ($234, 139.9× raw) is worth $207 more, so the difference comes down to the grade. The cheapest PSA 10 copy we matched on eBay when we last checked on November 2, 2026 was $245, 5% above our PSA 10 market value of $234, so eBay offers no discount on this card right now.
About $1.67 raw, $20.03 in PSA 9, $234 in PSA 10, based on our market values as of November 3, 2026. Its market value is down 10.2% over the last 30 days, from $1.86 to $1.67.
On current values, a PSA 9 ($20.03) is worth $6.64 less than a raw copy plus a $25.00 grading fee, while a PSA 10 ($234, 139.9× raw) is worth $207 more, so the difference comes down to the grade. This ignores gem rate and selling fees, so treat it as a best case.
The cheapest PSA 10 copy we matched on eBay when we last checked on November 2, 2026 was $245, 5% above our PSA 10 market value of $234, so eBay offers no discount on this card right now.