Shattered Kingdoms

Is there a way of [easily] finding out the relative wealth of a nation in comparison to others?

I think that currently only tribunal leaders have access to see their own kingdom's wealth, what remains in the safe, what was spend for defending against attackers and who was that, and so on.

Still, even they cannot see their kingdom's wealth in comparisson to other kingdoms so the general answer to the whole question would be, No.

You can get an idea of what kingdoms are in recession or depression by what items sell for. Sure, that also depends on the buyer, but if even the best dealer in the kingdom is giving you a rotten deal compared to other kingdoms, the economy's in trouble.

Likewise, if monsters start giving you half the usual gold - the country you're in is probably in recession.

It's hardly a precise measurement, but it at least gives you an idea. And economies don't change much day-to-day, so once you've done your research, you don't have to repeat it often.