Which Metagross ex do you have?
Same name, 12× the price: $11 to $125 raw. The difference is printed on the card — it is just not somewhere most people think to look.
Hidden Legends · #95
Check the set symbol in the lower right of the illustration, and the copyright year along the bottom edge. Those two identify the print run on every card that has them.
$125
13% gem
Power Keepers · #95
Check the set symbol in the lower right of the illustration, and the copyright year along the bottom edge. Those two identify the print run on every card that has them.
$81
8.2% gem
XY Black Star Promos · #XY34
Check the set symbol in the lower right of the illustration, and the copyright year along the bottom edge. Those two identify the print run on every card that has them.
$11
0.8% gem
XY Promos · #101
Check the set symbol in the lower right of the illustration, and the copyright year along the bottom edge. Those two identify the print run on every card that has them.
$11
82% gem
We have no hand-checked note for these printings yet, so the guidance above is the general rule rather than something specific to this card.
Prices are raw market value. Click a printing for its full grading verdict — the gem rate, the fees and whether it beats selling raw.