Even if you're "just" a 500 people company, expect the investment into getting a new hire up to speed to be at least a year's worth of salary - initial recruiting cost, dealing with governmental bureaucracy if the employee doesn't have citizenship, actual learning / training / handover time and reduced productivity in adjacent people.
Unfortunately, for most companies only the recruiting cost shows up in their HR budget calculations, so there is no "incentive" per se for HR to look for "leaders" who manage to burn through entire teams worth of people in years. They may achieve stellar business results, but the cost to the company doesn't show up on anyone's radar until enough people dump annoyance in Glassdoor.