"He should realise there are many native teachers of English in China living well off 4000 to 5000 RMB/month."

Yes...but the homies have family support, some social benefits in many places, bank credit, and other things that help offset the lower salaries. They also tend to live much more simply than most non-Asians do...and from what I've seen, tend to live relatively boring, home-centered lives that most of us don't come here to do.

It's really, really hard to compare what the Chinese need to earn in salary, to what any foreigner is likely to need.

Foreign teachers CAN live OK here on 3500 RMB a month (although I couldn't)...but generally NOT if they also have to pay rent, unless they either take horrible tiny ratbag apartments or they're in a really depressed economy where housing is dirt cheap (and there still are a few of those in China, deep in the hinterlands...).

4000 RMB a month with no housing provided, for a foreign teacher working full time, is unconscionable...native speaker or not. This is exploitation of the lowest and nastiest sort. A lot of non-native speakers have a rough time of it here, and a greater willingness to sell themselves for less, and less job mobility, than the native speakers, Many of the schools know this...and exploit it to the fullest. Non-native speakers CAN find better, but compared to native speakers it is more difficult- especially if the non-native speaker isn't white. Europeans (including Russians) generally do a lot better in China than their non-white Asian and African colleagues. Sad but true...