The Gardevoir ex (96 / 100) card can be found in the Sandstorm set.
Recently sold 6 times and based on those sales is worth around £20.10.
Currently, there are 9 open listings for this card on ebay.
This card sells in the range of £12.78 to £27.42, making it quite stable.
This Rare Holo Ex card was illustrated by Hikaru Koike.
The fact that it is a EX card makes it one of the more valuable cards.