Man, being the galactic trade hub (-10% market fee), Diplomacy Traditions (-10% market fee), and an import/export leader mandate (-5% market fee) = 5% market fee. All goods are essentially interchangeable to me now.
Anybody manage to get it down to 0?
The thing I found that really helped with unemployment was Commercial Zones, which give you 5 Clerk jobs for 1 building slot without requiring resources. Then as you get upgraded buildings (10 researcher jobs for one building slot? Don't mind if I do!), you replace them with other things.