In the years I was in mainland China (2003-2008), I made occasional attempts at changing locations, but fairly quickly I noticed a trend: Cities/locations that are most desired by foreigners (Suzhou, Hangzhou, Qingdao, Kunming, for example) are the ones that usually offer the lousiest contracts/terms. I recall that in Kunming the same teaching load I had in Nanjing which paid 8000RMB monthly (plus apartment allowance) at the time (2004-2006) was paying in Kunming on average, 3000RMB per month!!! And as Turino said, because a number of inexperienced FTs will accept these ridiculous terms, it makes it impossible for others to demand better.

I would also add that because I stayed in one city most of time I was able to keep my salary demands and expectations high because I had developed a strong reputation in that city among students, which was verifiable. About once a year, I would ask a few students to write letters (including telephone numbers) about my teaching style and personality in Chinese for potential employers to review before offering a position/contract. These letters were a key part of my negotiations. I never told students what to say, I simply trusted that their sincere testimony would be persuasive; certainly better anything I receoved from former employers/managers who usually had NO IDEA what I was actually doing in the classroom. If you work hard, students will often be your advocates. They always were for me, no matter where I taught -- and I worked in LOTS of different schools and situations.