Well, foreigners who work in shanghai earn more because their company pay more, and many Chinese who work in foreign companies get paid much more than those who work in domestic companies. and for english teacher, i heard they earn about 10000 per month , and it is less than those foreigners who work in companies, even less than some Chinese who work in foreign companies.
Think of it, it is always foreigner companies who pay salaries more than Chinese companies. is it equality that Chinese companies pay less for the salary? And it is not easy to get in foreign companies, really big competition, and it is not that people who get real talents get inside, sometimes it depend on your relationship with people inside. It is not real equality.