Base Set Professor Oak 88/102: PSA 9 vs PSA 10
Base Set Professor Oak 88/102 shows a meaningful PSA 10 premium between PSA 9 and PSA 10: a $71 dollar gap, with the gem mint multiplier at 2.8x. Based on the most recent PSA 10 sale of $112.50 on May 21, 2026, the math leans toward holding the 9: expected value turns negative at conservative upgrade probabilities once the resub fee is in.
PSA 10
$109.58
Last sale $112.50 on
PSA 9
$38.50
Last sale $27.00 on
PSA 8
$26.92
Last sale $22.84 on
The Spread
The PSA 9 to PSA 10 spread on Professor Oak 88/102 (Base Set).
$71
Dollar gap, PSA 9 to PSA 10
2.8x
PSA 10 sells for 2.8x 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 88/102 Professor Oak is a WOTC-era release from 1999. The gap between its PSA 9 and PSA 10 prices is $71.
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