All your Office 365 licenses for the tenant will be pooled together. Office 365 does not operate in terms of separate subscriptions like Azure does.

Do you have the department field filled out for your users in Office 365 (Azure AD)? If so, you could use a PowerShell script or even a custom view in the Admin portal to view the amount of users licensed per department and what license they have.

The costs are not listed anywhere in the portal however as that is not information that Office 365 always has access to (different customers get licenses different ways). You'd have to do that math by hand or build it in a PowerShell script.