It’s the best of times and the worst of times for the musical theater scene in Los Angeles. On the one hand, the quality of local productions is way up in recent years, and there seems to be no shortage of work for the area’s actors. But on the other hand, the cost of mounting such productions has gone through the roof, and there are even whispers that the business model may no longer be viable in the longer term. Still, in an era when many sectors of the American cultural scene are struggling to survive, L.A.’s theater crowd is learning to adjust to new realities.