Thanks for the info re the gulf. It seems workaholic males who need neither female company nor alcohol are best suited for that kind of work. Back in the 1970's qualified secondary school teachers could earn 10,000 GBP a year there tax-free, which compared favorably with said teachers' starting salaries back home of 5000 GBP a year. But even then, gulf salaries were on a downward spiral. Applying the same criterion to today, one should be on 36000 GBP a year there. Then it would be possible to live frugally for two years there in order to buy an average semi-detached outright back home thereafter.
That would be equivalent to around 58000 USD a year earnings, tax-free of course. But 3500 USD a month is only 42000 USD a year, which is not very attractive given the heat, the lack of freedom, and unfriendly colleagues there, etcetera. Clearly the downward spiral in salaries has continued. Not worth it to go there and have to work hard for so little, relatively speaking. Better to stay in China and get paid basically just for turning up at the classroom!