Final answer:
Comprehensive health insurance is typically the most costly benefit for employers to provide, especially due to the employer mandate requiring large employers to offer health insurance to their employees.
Step-by-step explanation:
The benefit that typically costs an employer the most to provide is comprehensive health insurance. Health benefits can be a significant portion of an employee's total compensation, often coming with high premiums for the employer, especially under the employer mandate, which requires all employers with more than 50 employees to offer health insurance. This is in contrast to other benefits such as paid vacation, $50,000 term life insurance, and paid sick days, which typically represent a smaller percentage of the total compensation compared to health insurance costs.