World Championship cards have little value.
They are from a deck that has a set population of cards. They do not share any of the rarity of their regular version counterparts.
For the WC cards to have value, they would need to be kept complete with the deck that they came from.
Now, I will say that there are people ripping others off on eBay by selling WC cards as if they were their valuable counterparts.
But those are fraudulent sales.