In the API docs I have seen a lot of fields that contain this phrase, for example:
priceWithModifiersAndItemAndOrderDiscoun int64 Price of item after adding all modifications and subtracting all line item and order level discounts. This is used only for reporting.
As far as I can tell from using the API in sandbox to create/lookup orders and payments, in practice this means "this value will be null".
Under what circumstances are these values populated?