Oberon VI was a rather high-tech and developed world by the standards of the region, which is still not saying much (look at TTS: Butte Hold for a comparison). The Class B HPG is unusual for an independent Periphery world. Unfortunately, the population numbers in Periphery 1st Ed are just a little suspect, and I don't belive that there has been anything newer printed since.
My best guess is the "electronics and pharmaceuticals" as mentioned above. I'd also imagine that, at least until their destruction, the Oberon Guards were in generally better shape and had better support and maintainece then the average pirate force in the area. Which again is not saying much.