I'm here to help you compare your sales and materials purchase, Brnstrmr.
You can run the Purchases by Product/Service Detail and Sales by Product/Service Detail report. Then customize the report to show only the information you need.
Another way is to export both reports to an Excel file so you can manually track and compare the sales and purchases of the product.
For your reference, you'll want to add inventory products in QuickBooks if you want to track inventory.
Keep in touch if you need further help with your purchases and sales. I'll always be right here to help you anytime.