Hi there Marche Mates
Thanks for reaching out about your users. QuickBooks Desktop is a great tool able to help you keep track of the financials of your business all from your computer. I can point you in the right direction for assistance with your users and their permissions.
To know if the cost of a product can be hidden from certain users, I recommend reaching out to the QuickBooks Desktop support team outside of the Community. They'll be able to assist in user customization to see what can be done to limit the users' view of the costs. You can reach them using the methods outlined in the Intuit Canada QuickBooks Desktop software support policies.
If you have any other questions, feel free to reach out here.