The value of the coin is given for business accepting WDC as payment. If tomorrow you can get a 7950 for say 1000 WDC, then there is the value: 1000WDC = AMD card.
No others currencies involved, no dolar involved.
Exchanges are for speculators, and they need a "price" (not value) to buy and sell and get the profit.
definitely agree what stated here.