Discount percentage of the list cost on a purchase order can be found in Vendor’s settings.
By creating the decimal attribute Disc%, you will be able to specify a value that an individual SKU will be automatically discounted on a Purchase Order.
When you add the SKU to a purchase order you will then see the value that you entered in Disc% attribute applied to the SKU.
Same as Disc%, you can use Extra% attribute for individual SKU to add extra cost on top of list cost or discounted cost.
In this example, Extra% is set to 30%.