What I've done to try and account for this is to enter the task as a fixed duration of two days, non-effort-driven, and then tried entering the resources that will be involved, each at 50% usage. What I'm seeing is different values for their respective costs (in the "Task Information" dialog), even though their rates are all identical. The only thing I can think of that's different between the resources that seems to correspond to the different cost calculations is that they don't all have the same "maximum units." But why would max units enter into the cost calculation?
I've attached a picture of my Task Info dialog.
Help... Thanks in advance....