Creating an order that is based on a quote allows you to verify the quote to check for any errors.  

Aggregate Volume Discount
We have seen in the Volume Discount article that this type of discount works line item by line item. with some customers this could be a debate and some would prefer to change this behaviour:
Volume Discount should be calculated based on all instances of the same product (Quantity aggregation).
Fortunately the PSP architecture shipped with Siebel 7.8 and above introduces a new pricing engine. Since price calculations are done in Workflows and Business Services, we can change them.