I have 3 resources assigned to a task. It takes 30 hours total to complete the task.
Say one resource works for $10/hr, another $20/hr, and third $15/hr.
The cost should be $450 since everyone works 10 hours each on this task.
But MS Project is calculating a totally different cost.
  Microsoft office will  calculates actual cost values as you enter the actual work. In actual cost that you enter, you have to switch to manual calculation method so therefore, you should change the method. Try this,  on the Tools menu click options and then click the calculation tab. Enter actual cost manually. Actual cost are always being calculated by Microsoft office. In order to have the actual cost automatically and correctly calculated,set this as default. Never forget that if you don't use the manual calculation method the actual cost value that you enter are overwritten when the project is automatically recalculated the value.
