Weight decides the freight
Most goods from China bill on volumetric weight, because they are bulkier than they are heavy. Metal auto parts are dense enough that actual weight is usually the higher figure, which is why a parts estimate moves less between quotes than one for consumer goods.
The exceptions are body panels, bumpers, light housings, air filters and plastic trim. They are mostly shaped air, bill on volume, and can cost more to ship than to buy. Mixing dense and bulky parts in one shipment averages the difference out.
