We've introduced a new role permission that prevents staff from editing an appointment's price, while maintaining their ability to edit other aspects of the appointment.
It lives under Settings > Staff Management > Roles > edit a role > scroll to Appointments > 'Appointments: Manage reservation price and deposit.'
By default this permission is on for front desk or higher. To ensure staff can edit other aspects of the appointment, leave their 'View and Manage' permission toggled on.
Note: the 'Manage reservation price and deposit' permission will only have an effect if the "View and manage" permission is also turned on. I other words to give this permission to edit the price, both toggles must be on.