Make these markets non-static.. make the "supply/demand" augment these rates. Let the org pres decide which market to sell their notum to and choose when to sell. This will add more depth to NW on top of giving orgs a reason to have a base beyond "buffs" because it becomes a way to earn money for your members.
I would like to take a suggestion also and say for the first time ever lets factionalize orgs:
If all orgs were forced to select an RP based mechanic ie.. "Department in OT/ Legacy Clan / Local Law Government" then it would give this market some true dynamics in how the NPC's reacted to people based on their orgs actions. Lets say for example that a power org that is constantly killing the DB would loose standings with the DB and make any exchanges between said org and the DB drop dramatically but an org that has not killed the DB would get a better return from them.
Orgs who attack Neutrals will lose standings with ICC. Orgs that attack Clans lose standings with Unionists/clan reps.. Orgs that attack Omni will lose standings with Omni. This would make the actions of an org be held accountable in many respects.
Additionally, each of the various "Exporters" could have custom Towers/NW items that can only be accessed through gaining enough faction with that particular exchange group based on transactional standings with them. In short, constantly doing business with the same person has rewards that shifting around to the best market does not have.
I could go on about how important making organizations select an RP based legacy to follow could be for other future PVM content as well as PVP content but I think I have got the ball rolling in your mind enough for now.