Voltorb #21 from Roaring Skies is a reverse holo common card that currently sells for about $0.50 ungraded, with graded copies ranging from $12.50 at grade 9 to $31.78 at grade 10. A grade 10 copy sells for around $31.78, about 64× the $0.50 raw price, so high-grade copies are worth grading.