Which M Gengar-EX do you have?
Same name, 3× the price: $59 to $193 raw. The difference is printed on the card — it is just not somewhere most people think to look.
XY Promos · #079
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.
$193
57% gem
Premium Champion Pack · #049
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.
$109
68% gem
XY Black Star Promos · #XY166
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.
$99
3.1% gem
M Master Deck Build Box Power Style · #011
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.
$83
66% gem
Phantom Forces · #35
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.
$59
4.7% 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.