The Gengar & Mimikyu GX (164 / 181) card can be found in the Team Up set.
Recently sold 10 times and based on those sales is worth around £37.00.
Currently, there are 2 open listings for this card on ebay.
This card sells in the range of £29.53 to £44.47, making it quite stable.
This Rare Ultra card was illustrated by 5ban Graphics.
The fact that it is a GX card makes it one of the more valuable cards.