Rachel --
Excellent question! You use Material resources to measure the consumption
of supplies of all types. As you measure the consumption of supplies, since
you have a Cost rate per unit, the system calculates the costs for you
automatically.
Cost resources are something different entirely. Cost resources come in two
varieties: Budget Cost resources and Expense Cost resources. You use a
Budget Cost resource for entering an overall budget for the entire project,
and you can only assign a Budget Cost resource to the Project Summary Task
(Row 0 or Task 0). You can assign Expense Cost resources to individual
tasks, to Milestones, or to Summary Tasks, depending on how you want to
track expenses. You can use Expense Cost resources in several ways:
1. You do not want to use Standard and Overtime Rates for resources to
track your overall project costs. Instead, you enter $0.00/hr. in the
Standard and Overtime Rate fields for each resource, and instead, assign
Expense Cost resources to summary tasks and enter actual expenditures for
the Expense Cost resource on every summary task.
2. You want to track individual types of expenses in your project, beyond
the use of Standard and Overtime rates. For example, you have a number of
tasks which will accure travel expenses for the resources assigned to the
tasks. You assign an Expense Cost resource to each of those tasks and can
enter the actual travel expenditures on the Cost resources.
So, as you can see, Material resources and Cost resources are two entirely
different things, each with its own preferred uses. Hope this helps.