FO1 take home pay is around $60K-$70 HKD per month before tax. Do not expect to earn any significant extra flying hours as this is inconsistent and the roster is not stable. If you have a family, or want to have a family, expect your monthly rent to be 40%- 50% of your monthly salary. Schools fee's at most international schools are around $185K -$250 per year, per child (not including extra curricular). Cost of living is quite high, but its on par with other expensive cities. Public transport is cheap and you don't really need a car in most areas. If you do need a car, its expensive. Your spouse or partner will need to work and if you have a family, you will need a domestic helper unless you have family in town to help.
If you are young and don't have (or want) kids; or you do have kids but don't have a brain then its worth a go if there is literally nothing else.
A lot of people have left Cathay because they could no longer afford it, but there are those who have soldiered on and have been able to stay on this poor contract by supplementing their income with Uber driving, doing Deliveroo or starting an OnlyFans.