Worth of coins in circulation

I think it would be cool to have the circulation value of the coins we have in our collection as data in the my coins section

For example if I had 1 2 euro coin and 1 1 euro coin my profile would show that I have 3 euros. The currency to be used to show the date could be the currency the person has picked to show bullion values of gold and silver coins. Would it be hard to keep track of exchange rates in this way using an automated system?