Hi All,
I am relatively new to Microsoft Project. I use Project for software implementation projects, from small to medium size.
I understand the mechanics of input, and for the most part things have gone fairly well.
One issue I am having is in costing for tasks when there are more the 1 resource for a task.
I've noticed the costs not agreeing with what seems to be the same calculation in Excel.
My concern is I may be missing something simple due to my inexperience in using Project for the budgeting of my projects.
I am using Microsoft Project 2016. I've also installed the trial version of the Project Professional installed today 2/8/2020.
I've created a simple project for test purposes, and have also created an Excel worksheet to check my calculations.
I have a task for 1 resource named P-1, with a resource cost of $146.00 USD. The task has 480 hours of work.
Project calculates the total cost as $70,080.00 which is correct.
I have a task for 1 resource named G-1, with a resource cost of $20.00 USD. The task has 480 hours of work.
Project calculates the total cost as $9,60.00 which is correct.
My third task is where the calculation is incorrect as explained below.
My task 3, with 2 resources, P-1 used for 60% and G-1 used for 40% displays a cost of $39,840.00 which is incorrect. The real cost should be $45,888.00.
Resource sheet is below. Yes they are over-allocated.

Task entries showing costs below

Task information showing the units below

My concern is I am overlooking something obvious to more experienced people here in this community.
Any help, coaching, etc will be much appreciated.