Production order cost calculation error

@Skn, your screen shots do not illustrate anything. The first shows a spreadsheet, which is completely irrelevant to Manager. There is simply no connection. The second shows part of a production order Edit screen, which contains no cost information. In other words, you have not furnished any information to support your claim that Manager is calculating the wrong cost of a production order.

You would need to show shots from the Inventory Items tab listing the average cost of the finished item. Then drill down on the total cost of the item to see what makes up the total cost.