Lines Drawn in Starlight

In fairness, the comment was that they do not have intrinsic value. Even then, though, as you say, since the market is largely controlled by a single entity, it does lend itself to some massive oversimplification and incorrect assumptions. One data point is not enough for understanding.
How would the price change, if there were multiple competing companies?
(or,... what if one particular clan of dwarves controlled all of the Admantine mines..?)