Applicant wrote that:

In fact the Foreign Affairs person (at a school in Yuncheng) I spoke with said that they would gladly offer a higher salary but when they tried this they received unpleasantries from the local competition so I think it is in fact Yuncheng English Village that is artificially keeping salaries low in the area.

This hard salary cap is confirmed.

Yuncheng English Village told past teachers that they would never be paid more than 7000rmb per month and that if they worked long enough that the annual rises would simply cease and salary capped at 7000.

Those "unpleasantries" likely included Kray-ish behaviour directed at Yin Xing.