I am sure you know about demand and supply. If the demand for highly-skilled labour is high, then I am sure you can easily find a job. In truth, I think it's the opposite in many countries. In addition, the definition of skilled labour is vague. Does one who has more work experience qualify as a skilled labour compared to a PhD fresh graduate in the job industry? I am sure most would agree work experience is still more important than your PhD degree.

In my opinion, most companies are seeking cheap and experienced labour. If degree holders can do what Masters, PhD can do in their line of job, should I hire someone who is overqualified and pay him more just because he has a PhD but has very few years of work experience?

Furthermore, climbing up the education ladder is an opportunity cost. You are giving up working experience which is highly sought after in the industry for education.

I would say, doing postgraduate will not guarantee you better income neither would it guarantee you a PR (well, nothing is guaranteed in life). In fact, you overqualify for many types of jobs and PR are highly dependent on the specific country's conditions.

80% of American PhD holders are doing work that are unrelated to their PHD scope.

I think this sentence needs more consideration compared to the job prospects. obviously high qualification = high job prospects.
But is it related?