Magmortar #DP20 from DP Black Star Promos is a reverse holo promo card that currently sells for about $3.58 ungraded, with graded copies ranging from $6.13 at grade 7 to $850 at grade 10. A grade 10 copy sells for around $850, about 237× the $3.58 raw price, so high-grade copies are worth grading.