Any large company puts all their records in an accounting system so they can figure this out. It make take some time to run the right query, but they have the records. Of course this assumes they put the full breakdown in the system, if it is just the total cost of goods including shipping as a single line item they can't do this - but commonly they will have the break down in some system. (at the very least the shippers/importer will - and they have incentive to run this for you and give you the results - it is fairly cheap and generates goodwill)