Well, I don't know if they really meant rack-mount gear, but sure it costs a little extra to get it usable with a general-purpose computer. Specifically, you c

Well, I don't know if they really meant rack-mount gear, but sure it costs a little extra to get it usable with a general-purpose computer. Specifically, you can get that Microchip HSM in a form factor that plugs into a click shield, then plug the click shield into a Raspberry Pi's GPIO pins. You now have a PKCS#11-usable HSM from a Pi. Including the click shield still puts the cost at <$20. (I have a few such setups lying around because my $dayjob includes a PKCS#11-consuming application that runs on such setups.)