Right now, however, it would depend on what exact Charizard EX card you are talking about, because there are several. Some are worth hundreds of dollars, but others on the other hand are only worth a couple of dollars.
If you have defeated the Elite Four and have the National PokeDex, on Wednesday tune in to the Pokemon Music station and look around. ( I did this and i found a lot of Pokemon from Holenn. Ex. Absol, Spoink, Numel, Plusle and Minun.) I hops this helped. ^_^