Base Set Onix 56/102: PSA 9 vs PSA 10
On Base Set Onix 56/102, PSA 10 sells for 5.3x a PSA 9, a $108 delta, which is an unusually wide gem-mint premium. Based on the most recent PSA 10 sale of $142.69 on May 27, 2026, the math leans toward holding the 9: expected value turns negative at conservative upgrade probabilities once the resub fee is in.
PSA 10
$132.90
Last sale $142.69 on
PSA 9
$25.00
Last sale $25.00 on
PSA 8
$18.25
Last sale $22.50 on
The Spread
The PSA 9 to PSA 10 spread on Onix 56/102 (Base Set).
$108
Dollar gap, PSA 9 to PSA 10
5.3x
PSA 10 sells for 5.3x a PSA 9
Three-Outcome EV Calculator
15%
70%
15%
Defaults are conservative starting points. Adjust based on the specific slab. A borderline 9 with strong centering plays differently than a 9 with edge wear.
PSA 10 outcome (sale price minus resub minus acquisition)
$0
PSA 9 outcome (regrade, no upgrade)
$0
PSA 8 outcome (downgrade, slower sell, tied capital)
$0
Expected Value
$0
Math favors holding the 9
Base Set 56/102 Onix is a WOTC-era release from 1999. The gap between its PSA 9 and PSA 10 prices is $108.
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