why is fly gear so darned expensive?

Because people are silly enough to pay an extravagent price. Fly fishing is associated with the upper class, and people spend money on fly tackle exactly as they would on a prestigious car, to show that they have the wherewithall to do so. True, fly reels are made in small volumes, but that's because they are so simple, compared to other reels, that any machinist can have a go at building his own. Ask any rod builder; a fly rod is the simplest of all rods to build. It's the social politics that make it expensive.