Yep, the only thing with an actual value is cash backed by the government. with all else, the price is dictated by the market.

A 1952 Mickey Mantle Rookie card (or a T206 Honus Wagner card for that matter) has an actual cash value of fractions of a penny based on actual cash value of the materials that are in the card. However, as a collectible, people are willing to pay far more than the actual value of the assembly components of the card because there is a perceived value as a collectible, a personal value for a particular person, or any other reason. The value is dictated by what somebody is willing to pay for it. In the case of a "common" collectible, it is relatively easy to determine what the market price is because numerous items are sold in a short amount of time. but, for more scarce items it's harder to determine the true market price. If only one exists and it was last sold 10 years ago what is the proper price to ask? who knows. the price for today will be whatever somebody is willing to pay for it, today. You see this all the time in the Christi's auctions. an item will have a pre auction estimate of $100,000 and then it will sell for $400,000. Sure, some of it is auction frenzy so the true value may still be lower than the purchase price but there is no way of knowing what the market will bear.