Tough question, but here's a generalization from my experiences:

Full Expats get at least $100,000+/year and usually the cost of housing covered. Often, if they have families, their companies will pay $25k or so per year for international schools for their children. Each package is different, but I think this is a good average.

International school teachers vary a lot. I knew someone who was making about $75,000usd a year, I've known other people making about $30,000usd/year. Depends on the school and experience/degrees, etc.

Other English teachers get between $10-20k.

Locally hired expats (half-pats? me included) between $15 -$75,000, but I'd say the average is between $20-35k. Again, depends on the industry, experience, degree, etc

These are just generalizations on my part based on my experience, but I think they're fairly close.

If your talking about average compared to Shanghai and Beijing they will both be around the same average. Depending on the type of job you have and your position. 

Somebody with a Masters should be getting a little more than someone with a Bachelors and someone with a PH.D should get more than someone with a Masters. 

It doesn't always work out that way but still on average between the two cities it will be about the same. It also depends if you have jobs on the side like tutoring, grading essays online or doing part-time and full-time jobs simultaneously. 

Depends on the job. Intern, Teacher, Profession. I could help you more if you elaborate. The pay is much higher in all aspects in Shanghai, but then again the living is 10 times as much as any other major city in China

 it depends on what job you want to apply for but if teaching, it depends on how many teaching hours or periods you will have. But there must always be basic salary..