I wonder how much money do you earn at school now. I don't think 3500 RMB. It's a good salary for chinese english teachers but not for foreign teachers. We are foreigners here and we are not at our own country. My chinese friend is an english teacher, he has been teaching over 20 years and he earns only 4000RMB and he says that its not enough for him. The prices on food getting higher day by day even in China. (eggs, meat, etc) I think a foreign teacher deserves higher pays. Regardless he is a native speaker or not, 5000 RMB at least.
see this site http://www.teachabroadchina.com/can-non-native-english-speakers-teach-in-china/
posted by filipino teacher earning 8500 RMB a month plus 150 yuan per hour for extra classes.