These are the questions being asked, as they have been for decades, as employers struggle with a decreasing pool of talent and increasing business needs. The costs of replacing a lost employee can be staggering. Costs can be as much as 3x base salary for a mid-level manager.
Formulas abound for calculating replacement costs.
The Saratoga Institute offers a commonly used one. There are others that are less traditional. But any way you calculate it, turnover costs money. Some turnover is probably unavoidable. This is the kind of turnover caused by people getting married, moving to be nearer parents or children, employees leaving for medical reasons, etc.