Base Set Koffing 51/102: PSA 9 vs PSA 10
The PSA 10 to PSA 9 spread on Base Set Koffing 51/102 is a meaningful PSA 10 premium: $81, with PSA 10 copies trading at 2.8x a PSA 9. Based on the most recent PSA 10 sale of $125.00 on May 29, 2026, the math leans toward holding the 9: expected value turns negative at conservative upgrade probabilities once the resub fee is in.
PSA 10
$125.00
Last sale $125.00 on
PSA 9
$44.43
Last sale $40.98 on
PSA 8
$26.98
Last sale $33.30 on
The Spread
The PSA 9 to PSA 10 spread on Koffing 51/102 (Base Set).
$81
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
Where this card lands in the broader Base Set picture: a WOTC-era card carrying an $81 gap between PSA 9 and PSA 10, a 2.8x multiple on the PSA 9 price.
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