Twinborn

A few things to note. First off, soulcasters are not mostly used in remote locations. The Azish don't use their bronze soulcaster in remote locations, they use it to make their capital look all bronze-colored. Kholinar (not a remote location, but rather the capital of the largest country on the planet) has been stated to rely on soulcasting to provide a portion of its food. We know that there is a significant farming industry based off of farming gemhearts, and it seems unlikely that the merchants would all be making money off of the trade of these gemhearts but the King (who owns all the soulcasters in Alethkar through the ardentia) doesn't get his own cut. The King wouldn't be buying heliodor from gumfren to produce soulcast meat in Kholinar unless he could make a profit off that transaction or if it was absolutely necessary to avoid a famine (and we know that, while Soulcasters are the economic option, Northern Alethkar food production could provide sufficient food to maintain Kholinar without soulcasting). We know that with regards to other ancient artifacts (Shardblades and Sharplate) the Alethi Royals are always trying to turn a profit by renting it out at high prices, so it seems reasonable to assume that they charge significant fees for the use of their soulcasters. Additionally, if Jah Keved doesn't have a large supply of stone soulcasters capable of producing various valuable kinds of rock, and have a high demand for them, then the price of, say, marble in Jah Keved could be largely disconnected from the soulcasting industry. Soulcasters are rare artifacts from thousands of years ago, not every location has a soulcaster to produce everything.

We have no evidence that, say, 1 emerald broam could be used to make an average of 1 emerald broam worth of grain if used in a soulcaster. There is probably a sizeable markup, which is where Lin Davar's income comes from. Its like how if a woodcarver makes something, they can produce a profit even though they had to spend money to buy the wood in the first place.

Can First of the Sun creatures read minds/detect emotions at all? You might be able to spike something out of one of them if they can.