Go to Setup > Clerks > Add/Modify > POS > Default Price Level.
Any clerk that is also linked to a User account that has modified the Price Level Permissions will also be affected.
Go to Setup > Users > Add/Modify (other than Admin) > Clerk Permissions > POS > Price Levels.
Clerk/User Permissions will not override the Default Clerk Price Level.
Where the Clerk/User Permissions Price Levels behave differently to other price level changes, is that they will display a warning message when the new Price Level is unable to be used by that clerk.