Ben,
Did you ever find a solution for this?
I found that using the Data Source - Profitability Order Profit and incorporating the Price Component field to establish Discounts (2/0007), Cost (2/008) and Sales Amount (2/7PR1) provided me with the ability to create a Sales Order Report showing, Gross Sales Amount, Order Level Discounts, Line Item Discounts & COGS. Throw that into a pre-formatted EXCEL Add-In Spreadsheet using a pivot table to summarize and calculate the Net Profit and Profit Margin and you'll have the full picture of Order Profitability.
Regards,
Curtis