The current licensing on Dynamics 365 Human Resources (as it is in July 2021) is as standard $120 per user per month if HR is your only Dynamics 365 app. If you have other apps and those same users will have access to HR, the cost is $30 per user per month.
That cover the users that needs the full access to the system and all the operations in HR. Now we can move on to all your employees and managers.
You might have several users with a Team member licence (8$ per user), these will already have access to the employee and manager areas in HR.
If you have user with the Activity Operations license ($50 per user per month) also they get the same access as team member licensed users.
If you have employees that just for everyone that just needs the Self Service capabilities, both the employee and manager. You can buy the Self Service license for just $4 per user per month.
Don’t forget that with your HR license you get 2000 Customer Voice reponses per tenant per month!