Ok, so I'm getting a little bit bogged down now. 
The problem seems to be the way you gain information on the prices of objects, you actually have to be at the planets.  While this might not sound like a real problem, there is also no autopilot between systems, so trying to find a specific type of mineral at a good price can get really really boring sometimes.  This also applies to ships, as there is no way to view what ship is in the shipyards of each city, so I'm sill on the einhorn (Ace Ventura reference?). 
Pretty much have just been flying around looking for Adelaide Medicine on the cheap...