I'm flying a 300 in Idaho Part 135, and I'm getting lowballed being paid in the mid-30s; however, for SoCal, I would venture to guess around 50K would be average for that area. On one salary survey I've seen, the average King Air Captain pay (no model specified) was 47K. Maybe Im being conservative by saying 50K, but with 135, it always seems to be lower than what you would think (for me anyway.)
Hope this helps you.