You might want to clarify what you are looking for exactly. At first you mentioned MBEWH, which is a standard price history. Of course, it's only by period because that's how standard price is maintained. Then you're saying you want to see "changes". But that's the whole other set of data (= change documents, which are not available everywhere, as Raymond correctly noted). Then in another comment you're saying you need purchasing price. But that's the whole other story and different set of information. Kindly be more specific.

Also reach to a functional consultant for more information on the business requirements. You can usually find the source tables using SQL trace and a transaction where data in question is displayed. But it's not clear in this case what you're looking for.