How to calculate the sale order item costs?

1.In sale order type definition or in reruirement class ,you can define the Condition type for copying costs from line items.
2.Define the costing variants for product costing

The following is where you enter the condition type which you want to use to determine the results of the sales order pricing for a sales and distribution document item.

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Use
If you enter the condition type into the requirements class, this condition type is used for all sales and distribution document items containing a requirements type, which indicates this requirements class.
The definition of the condition type per requirement class allows you to determine different condition types for the different items of a sales and distribution doc. For example, you could carry out pricing for one item on the basis of a sales order pricing procedure, while the value of the sales order pricing might only be forwarded statistically for another item in the same document. The sales order costing refers to the sales order item.
If you enter the condition type into the sales document type, this condition type is used for all items in a sales document of this sales document type.
In the standard version of the SD system, two condition types are provided for the cost transfer of line items:

EK01
If you choose this condition type, the result of the sales order costing is first printed to the pricing screen for the item. The value can be used as the basis for price computation.
EK02
If you choose this condition type, the result of the sales order costing is simply a statistical value, which you can compare with the price.
Dependencies
Take the following points into account:

The condition type must have condition category 'Q' (costing).
The condition type must agree with the condition type defined in the SD pricing procedure.
If you also want to display the fixed cost part in the condition in addition to the full costs, then enter a condition type in field "CondTypeIndFix".
The transfer of the fixed cost part improves the ability of the system to predict the profit margin.