The NPCs spend years practicing their Glass-Blowing skills. The PC overtakes them because they kill lots of goblins. Right, that's not at all unreasonable, but having people excel at their profession without also being high level is.
The solution, to me, is an NPC class specifically designed for gaining skill in very focused areas. Perhaps this NPC class gains no BAB, no save bonuses and no hit points from levelling up. Maybe all he gets is an enhancement to that one professional skill, or maybe he gets another skill point or two every now and then. Or maybe levelling up gives him higher income potential in his chosen profession. It's an NPC class. It doesn't have to be as good, or nearly as good, as a PC class.
Which means that PC's are special, to some extent, from the outset.