The Gengar (27 / 130) card can be found in the Diamond and Pearl set.
Recently sold 5 times and based on those sales is worth around £5.60.
Currently, there are 2 open listings for this card on ebay.
This card sells in the range of £0.02 to £11.18, making it quite stable.
This Rare card was illustrated by Kagemaru Himeno.