The most important thing in a coin is the opportunity to use it in the product ecosystem. If the coin is made just for fun, then, of course, it does not cost anything, because any currency, digital or fiat, must be provided with something. There are good coins that were invented to use as a payment and be the part of project ecosystem. Such coins will always be in demand and well traded on the exchange. Those coins that made only to attract money or just for mining will cost nothing. The coin will be successful if it has meaning and demand.