Bronzong #XY21 from XY Black Star Promos is a reverse holo promo card that currently sells for about $7.70 ungraded, with graded copies ranging from $29.99 at grade 9 to $107 at grade 10. A grade 10 copy sells for around $107, about 14× the $7.70 raw price, so high-grade copies are worth grading.