I would suggest looking up on eBay so see how much people are selling their Pokémon cards and start from there.
I have a bookfull of the original Pokémon cards that first came(like a 1st edition Zapdos, holographic and a Charizard) out and I don't think they would be worth much since they don't live up to the new rules of the tournaments that the cards don't have themsevles but the new cards do. I read that off of a respone on Yahoo Answers.