The Gengar (13 / 165) card can be found in the Expedition Base Set set.
Recently sold 3 times and based on those sales is worth around £40.10.
Currently, there are 3 open listings for this card on ebay.
This card sells in the range of £32.02 to £48.18, making it quite stable.
This Rare Holo card was illustrated by Yukiko Baba.