I have about 20 jumbo cards, I've had them since a month ago (February) and I really want to know how much they are worth, since they cant do anything in battles I want to sell them.
So by looking through eBay, (probably the best Pokemon card selling place on the internet,) I can see that the cards are worth about maybe 2 or 3 dollars on average. This is probably because they are promo cards and can be easily found at any Pokemon card selling location. I would probably hold on to them for a while, because after a couple of years of them not being in the boxes at Target, they are going to become rarer and rarer, which means more valuable.
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