The Est. Extended Cost is a snapshot value of the item’s Cost Estimate Type which is taken upon the creation of the Sales Order transaction. The Est. Extended Cost may not be updated in the Sales Order even if there are new Purchase Orders for the item with Cost Estimate Type = Last Purchase Price. To check, you may inspect the PO creation date. The PO should be created after the SO, because the Est. Extended Cost is taken upon the creation of the Sales Order transaction. The Subsidiary in the PO is aligned with the Subsidiary on the SO.