I prefer being a senior middle school FT in China because it's money for old rope, and even less effort is required if a TA is assigned to you. Much better than jobs I could get in the West. Fact is, 16 X 45 minute classes/week for 5,500 Yuan/month with a rent-free flat plus travel allowance plus air fare allowance without marking homework without giving oral exams beats teaching high school in the west all ends up.

The problem here is there are too many expats who are so greedy for money that they will allow themselves to be duped by the Chinese side. BTW, I believe we should be teaching in China to chill out, not to work hard.

Do the math pro rata: 16/week = 5,500/month; just prepare 1 lesson plan/week. TA assigned to assist you.
So, 18/week = + 1/9 = 600 Yuan approximately. Total = 6,100 Yuan/month.
So, 20/week = + 1/4 = 1,300 Yuan approximately. Total = 6,800 Yuan/month.
So, 22/week = + 3/8 = 2,000 Yuan approximately. Total = 7,500 Yuan/month.

But Chinese employers do not like to operate pro rata nor increase hourly payments because of expats working overtime. They are more likely to reduce the latter to 50 Yuan/class!

Back home when I was teaching high school high, my timetable was 25 classes/week, I had to mark homework, set tests and exams, and mark them. I was teaching 6 different courses, requiring the preparation of 6 lesson plans/week. I also was expected to attend parents' nights for no extra payment. Not to mention having to discipline the disruptive children of the great unwashed. That's a crap job, given the salary offered. Teaching in China is much less stressful. You can even smoke on the school premises during breaks and drink beer before class without fear of negative repercussions, provided you're never half-pissed in class. Long lunch hours too, 2 or 5/2 hrs, not the stingy 60 minute lunch breaks, or even just 45 minute ones, that are standard practice in the West!