The most valuable card illustrated by Sekio is Caterpie (McDonald's Collection 2019) at $15, ahead of Magikarp ($13) and Lapras ($8).
Value counts each card once at its highest-priced printing. The homepage leaderboard additionally requires a priced rarity cohort, so its totals run slightly leaner.
By TCGplayer market price, the most valuable Sekio card is Caterpie (McDonald's Collection 2019) at $15, followed by Magikarp (Dragon Majesty) $13, Lapras (Lost Thunder) $8, Houndoom (Lost Thunder) $5, Eevee (Lost Thunder) $5. Prices are TCGplayer market for raw copies (any condition) and refresh daily.
TickerMint tracks 74 Pokemon cards illustrated by Sekio across 74 printings, with a combined market value of $80 counting each card once at its priciest printing.