I just wonder how much he knows about economics to not over saturate the other world's market with supplies from reality... and vice-versa.
In fact, you would literally HAVE to go into black market trading because of gold-silver prices over here.
It could crash global economies, hell even more-so, raise suspicion of mass market trading from a seemingly endless supply of gold and silver to get the attention of international powers.
But that's just me analyzing a realistic situation, I doubt the artist would go THAT deep into economics, not unlike Spice and Wolf.