Like most Pokmon cards, the value of Pikachu ex depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Ascended Heroes)
Specifically, the Sheldon's Spellbook cards centred around Commander and featuring references and tributes to Menery and his own favoured decks
Then, if you have enough mana in the same turn, you can quickly exile them so they arent issues anymore
Combo-oriented decks can rip through their list, and even fair decks will find plenty of card advantage and cost reduction from this vampire
This site provides comprehensive information about the card, covering everything from the set name and illustrator to the regulation mark and rarity
This card has absolutely taken over the most expensive Pokemon card purchases on eBay, selling for up to $25,000