Its only worth as much as someone is willing to pay you for it. Same goes for comics, cards, figures, etc.
I've had many items in the past that were worth a lot according to whatever official price guide, yet anytime I would try to sell them at a convention or what not, no one was willing to pay remotely close to the guide price.
My advice: put it up for auction starting at .99ยข. Whatever it ends at is what its worth.