The Skarmory ex (98 / 108) card can be found in the Power Keepers set.
Recently sold 5 times and based on those sales is worth around £21.39.
Currently, there are 7 open listings for this card on ebay.
This card sells in the range of £14.40 to £28.38, making it quite stable.
This Rare Holo Ex card was illustrated by Ryo Ueda.
The fact that it is a EX card makes it one of the more valuable cards.