Mewtwo & Mew-GX #SM191 from SM Black Star Promos is a reverse holo promo card that currently sells for about $315 ungraded, with graded copies ranging from $318 at grade 7 to $1,925 at grade 10. TCGrader's AI has graded 21 copies of Mewtwo & Mew-GX (SM Black Star Promos), averaging 8.3 overall. 33% scored 9 or higher, so a strong copy is achievable but far from guaranteed. A grade 10 copy sells for around $1,925, about 6.1× the $315 raw price, so high-grade copies are worth grading.