Your Captain is a "Spacer" and the men and women operating the Exchanges are "Gravs" or "Grounders" and there is a sharp and clear social and political division between these two classes. One of the most stark divisions is in regards to access to resources.
The "Exchange" that the Captain visits is a carefully regulated trade zone that is accessible to both Spacers (independent and reputable faction members as well) and (depending on local customs, rules, laws and traditions) any planet-side merchant with the necessary permits and contracts.
Shalun Law, which governs warfare, espionage, manufacturing, trade and criminal justice defines the rules of the Exchange and the role the Central Database plays in this system. All Trades in the Exchange are recorded and are public record to Spacer and Grav alike. Any who violate the laws of the Exchange can be banned for life or an edict of execution issued by the controlling Prince.
The Prince determines what is available in the Exchange, how much and when. Depending on Faction quotas, military requirements, local consumption very little or no goods may be deemed available to the Spacer Exchange.
In my mental model of the game, the Captain who "ends a shortage" has successfully filled a high dollar order from the Prince. It is the Prince, not the local merchants, who cools the prices.
Visit an Exchange, for kicks, while the Prince is in hiding. You may find some odd things happening ...