While I don't doubt the coins can influence others and the world around them, I am betting the whole meant to be in circulation must have been bolstered and inflated by nicodemus efforts.
The thing is while they are fallen, the denarians can be counted. We know they can be messed with using soulfire, and they seemed vulnerable in the presence of sword of the cross. Also, I wonder if they might have a similar vulnerability on demonreach, due to the fact they were slain there and it's protections are at least able to interfere with some abilities of the fallen.