Anyone who justifies foreign teacher's salaries by comparing them to local college gradates is high on some kind of chemical fumes.
Local people have credit. People who make 4000rmb/month are driving around in cars and buying houses. Most laowais have to pay in hard cash, have bills to pay overseas, pay for visas or visas runs, have to fork out money for international airfare, pay the "laowai rate" for lots of stuff, lack the connections or knowledgeable to know where the best deals are, often cook for 1 or 2 rather than a whole family, and need to have enough euros or dollars or whathaveyou in pocket when they leave Kunming so that they don't end up on the street upon arrival abroad. RMB doesn't convert very favorably.
They also have no job security or futures with the companies they work for while in Kunming. In short, many if not most non-trustfund, non tourist foreign teachers need much more money than most local workers. The question is not how much do they make compared to oca workers, but how much do they make compared to the school owners and the families that send the students to class.
I agree with Tigertiger about the press comments.