Managing cost centers by making them profit centers
https://techcrunch.com/2017/05/14/why-amazon-is-eating-the-world/
Amazon benefits not only from the revenue from externalising its internal services, but also from the efficiency and oversight induced as a result.
This is similar to the export-driven growth described in Joe Studwell's How Asia Works - East Asian countries gave domestic industries protected markets, conditional on their ability to export and hence prove that they were making goods that were competitive in international markets.