These situations can become traps for local economies: People don’t want to invest in education without job opportunities. Companies don’t want to invest in more jobs without educated applicants. Self-reinforcing cycle.

The inverse of this situation is why high cost of living cities continue to thrive: It may cost more to hire and retain people, but you’re guaranteed a supply of motivated and educated applicants. It becomes worth the premium to operate in those expensive markets.

I can’t speak to SA, but there are definitely cities and even regions in the United States that have high unemployment but also struggle to hire reliable employees regardless of wages offered. Even if a company pays well, the well-paid and well-educated hires often want to use those jobs as a springboard to move out of the city rather than risk tying their career to a declining local economy. Turnover is high simply because educated and motivated people leave the area.