During planning, when thinking through the resources that are needed, it is tempting just to consider people. But resources come in various other ‘flavors’! All of these contribute to the final cost of the project.

Similar to people, other types of resource may also have availability problems – not just their cost.

When performing cost (budget) planning, it is vital to obtain a complete picture of ALL resources. After all, the tasks don't consume resources - it's the resources USED to complete the tasks that consume.