Yes, the ability to view expense rates can be enabled or disabled via your user role configuration. To change the ability for users' to view expense rates, go to Settings, and then click User Roles. From here, click on the name of the user role you wish to modify. Jump to the Expense Permissions section and toggle the View Expense Rates permission.
Note: Limited access users can only view their own expenses and their own pay rates, regardless of this setting, so often times it is acceptable to allow investigators to view their rates.