I doubt your friend makes that much. If he or she does, it is because he or she works for a company not a school. Someone who makes that much is usually working for some big joint-venture company, such as in marketing.

You won't make that much teaching, no way. There are only a few exceptions and they require a degree. Such as director of studies for a big company like WEB English, a kindergarten teacher at a famous kindergarten, or teaching IB level(usually for one of these rich private schools that caters to foreigner's children).

Now, 7000 is not a problem, you can make that in many of the larger cities. But, the current rate is between 5000 - 6000 including accomidation. Beijing and Shanghai, you can expect the same, or you can choose to do your on apartment and make about 2000 more.

Some of the little villages, and not so modern cities will offer only 4000. Also the Universities and the more remote places will still offer only 4000. I don't know why so little, but maybe things are cheaper there, but I seriously doubt it is cheap enough to make such a big difference.

There are some serious imbalances in the pay rate scales throughout China. It is not a set standard that equals out evenly.

For example, you spend more living in Beijing, but you make more, in the end you will bank more.

Look at two ROUGH estimates:
A.
Working in Beijing:
salary base: 8000 per month
accomidation: 1600 per month
basic living expenses: 1800 per month
------
bank about 4600 rmb

B.
Working in Sichuan
salary base: 4000
accomidation: free
basic living expenses: 1000 rmb
-----
bank about 3000 rmb

SO you see, these are just rough estimates, just imagine some of the people whom make 10,000 rmb teaching per month, they bank at least 5000 rmb per month. It is not equal yet, so even if you spend less in another place, you will not make as much profit as you would if you lived in the metropolises. So it basically comes down to: is the money important or not? Do you want to live in a big city or not?

You can get good teaching experience and have a great job in either places.