For organisations with the resources to deal with an APT, great lengths are gone to in order to verify that the supply chain is trusted all the way down to the chip manufacturer. The hardware used isn't just bought from Best Buy and given a huge dose of trust, but instead there are with many many steps to verify that the eg the hard drives are using the expected firmware version. You spend as much as you can on the whole process, but if your threat model includes the CIA, China, and the FSB, it's exceeding expensive.