Ah, that depends on order volumes (overall, not average order size) and their warehouse set-up. And it depends a lot on how much you pay for shipment. That being said, there are automotive parts suppliers that ship, reliably, orders of 3 screws, two nuts and 4 washers. From the UK to the EU nonetheless.

I could imagine either dirt cheap labor in well laid out warehouses or some form of automated picking solution.