Yes, that’s true. In logical terms, you are absolutely right. But it is really much more complex than that.
I think some reasons the REALLY expensive ($20G/year) international schools charge so much is because:
a- they can because what other choices do parents have when they feel so out of place? Plus, to attend these schools, you HAVE to have a foreign passport, which means that most of the people who attend receive an education allowance that covers all or most of the tuition.
b- they generally build new facilities (as I said, SUIS is a Chinese local school with an international branch, which means it is not a western facility)
c- they import teachers so they have to pay them a lot more, packages etc… whereas the bilingual schools only import about 1/2 of their teachers, and the other 1/2 are local and don’t receive packages. YCIS is an exception to this, although they may import many of their Chinese speakers as well since they are a Hong Kong based school, I’m not sure.
I’m sure there are plenty of other reasons, and I’m not an expert. I am only making observations. It seems a very bad idea to assume that just because the school is expensive that they pay their teachers well, and that because they pay their teachers well, it means they are top notch. It is not always as it seems.
It is my opinion that quality teaching doesn’t necessarily have to do with how much you are paid, the facilities you are teaching in, or what country you come from.