The Blastoise & Piplup GX (215 / 236) card can be found in the Cosmic Eclipse set.
Recently sold 8 times and based on those sales is worth around £45.00.
Currently, there are 5 open listings for this card on ebay.
This card sells in the range of £35.25 to £54.75, making it quite stable.
This Rare Ultra card was illustrated by Akira Komayama.
The fact that it is a GX card makes it one of the more valuable cards.