Use the same scope
Compare the same quantity, specification, packaging and destination. Establish whether each quoted price includes transport and handling.
Separate confirmed charges from estimates
List the product cost, transport and applicable handling charges. Record taxes separately and ask your accountant how they apply to your transaction.
Include operational constraints
Storage limits, unloading access and delivery frequency affect the workable order size. Do not compare a full-load price with small deliveries as if they were the same service.