The administrator can control the field access for each individual profile and consequently the access for each user. The screens are exactly the same as in Section Default Organization Fields Access, but here the control is exercised not for all users but for a specific set of users as defined by their profiles - Settings -> Field Accessibility -> Click on specific module -> Select Profile.
Note: The "Unit Cost" field if turned off in the "Product Field Access" also turns off the display of the Unit Cost for the selected Profile in other modules like Sales Order, Purchase Order etc. where the Unit Cost would otherwise have been displayed.
Updated 5 months ago