One thing you seem to be forgetting in the ideas about randomized commodities is that different systems sell specific things based on where they are and what their part of the universe has an abundant supply of. It seems the commodity routes have been set up so the farther you travel with that full cargo hold, the more encounters you'll have with people who want to take it, but the more profit you make. Randomizing the commodities would be good, but would destroy the idea of what's made locally.

I tend to prefer rather the idea about setting up a dynamic supply/demand system where as an outpost or planet gets more of something it needs, the price drops dramatically, but over time, will rise again as the rescources are used up. The only problem with this is the amount of cargo any of the available vehicles can carry is miniscule compared to some of the super-freighters you find with like 40,000 units of whatever.

If you were to use the random idea, in order to maintain the idea that you travel further to find the best deals, it would be cool to randomize the values based on where the base is located. There are databases already that have outposts listed by system, and it wouldn't be too terribly difficult to set it up so commodities are randomized such that a near system wouldn't make as much profit as a far system while still making the player search for good trade routes. You'd still need some sort of dynamic system for changes values of commodities, however, because for a persistent server, there'd be a lot of maintenance required by the person running it in rebooting the server constantly to re-randomize the trade routes....

I'm rambling a little...but maybe these thoughts will help come up with the best solution...

All that is gold does not glitter
Not all those who wander are lost
The old that is strong does not wither
Deep roots are not reached by the frost.
--JRR Tolkien