A Work Breakdown Structure, in the 3D WBS model, goes up to the tasks. Activities are deployed on Products and Products are assigned to a Zone (it can be instantiated before). A Zone is a group of Products. In anotherwords, to do a schedule, you group the Products by Zone and you detail the Products by Activities. The schedule shows “how” you do the job.
For a Cost Breakdown structure, it is not the same. I mean for Direct material costs, Direct Labor, Manufacturing overhead, variable or fixed, fees, etc. To build a Cost tree structure, you group the Activities by Zone, and you detail the Activity by Products. You do that because you estimate the cost of SOMETHING. The Cost Breakdown Structure shows how much is the cost of “something” (Product).
Now, let’s look at the Cost Breakdown Structure in the project cube.
First, you group the activities by Zones.
Then, you deploy Products on activities, with different levels of details.
In 3D, you obtain this picture, it is not a 3D Gantt, it represents the Cost Breakdown Structure in 3D.
The Activities are more detailed in a WBS whereas the Products are more detailed in a Cost Breakdown structure.