Greninja-EX #XY20 from XY Black Star Promos is a reverse holo promo card that currently sells for about $9.75 ungraded, with graded copies ranging from $19.99 at grade 7 to $1,813 at grade 10. A grade 10 copy sells for around $1,813, about 186× the $9.75 raw price, so high-grade copies are worth grading.