Isn't what someone is willing to pay pretty much the definition of value? And I find eBay prices to be the standard. Every thrift store, pawn shop, antique shop, individually owned game shop, etc.. I've seen bases their prices on eBay. Casual customers walking into these shops may not be willing to pay these prices but the only reason that a shop owner would be willing to sell a game like Earthbound for less than $100 is because they're either the rare dealer that either don't know how much it will sell for on eBay or they do know but just want the quick cash. Lets be honest, when you go to a tag sale and find a game that you believe to be rare one of the first things that most people will do when they get home (if they didin't already do it from their phone while on the road) is to check to see what it's going for on eBay.