Answer
Latest Purchase Price and Average Purchase Price aren't updated automatically as purchase transactions happen — business users need to run the Calculate Purchase Costs engine for those values to refresh. Separately, for a part that's neither lot/batch-controlled nor serialized, Shop Order Backflush cost is driven by the Unit Cost shown on that part's Inventory Value tab, not directly by the latest purchase price field itself, so check that value if backflush costs still look wrong after running the cost-calculation engine.