In an agreement with a supplier a product can be added to an agreement item. As shown in https://demo-trunk.ofbiz.apache.org/accounting/control/EditAgreementItemSupplierProduct?agreementId=DS-1000-PURCH&agreementItemSeqId=00001
See image OFBiz-Agreement-Item-Products.png for the result.
When this is completed, the 'Supplier' overview of the product shows the product and its Supplier price is added.
See image OFBIZ-Product-Suppliers.png
However, as shown in the image, the previous price of the supplier is not expired.