I think that it would be really cool if Nation States made a feature which shows the value of a nation's currency. Oh man, that would be sooo key!
Just use an economic calc. i dont remember the exact site adress of the one I use, bu tyou can find it if you type in:
In google. First link.
NationStates Currency (http://nseconomy.thirdgeek.com/)
Our currency is called WW$ETI and many of the regions nation is using that.