User Roles can be set to hide cost prices from view.
1. Main dashboard timeline
2. Users personal activity feed
3. Dashboard against the product
4. Costs against the product under Prices & Costs tab
5. ACP KPI from Dashboard of the Product
6. Supplier tab of the Product
7. Order Lines
With order lines they will display the cost field if it is for a special product, or the Stock Source is set to a linked Purchase Order, Back-to-Back Purchase or Direct-to-Site Purchase. Then the user needs to see the cost field to set the associated purchase price.
Setting the User Role
For Users with access to Settings > User Administration > User Roles
Double click on the appropriate role(s)
Under the Sales Module deselect 'View costs'