Let's say you're a fairly talented individual with Linux, with hardware.
You have to buy parts, ship them in, install the OS, build a web gui
for the OS, stick it all in a 2U height device, burn a failsafe kernel
to a ROM (for backup /boot loading), and configure squid/apache/mail/dns
etc. Make the OS invisible, so it's fairly user-hidden, and make the
entire thing re-configurable within 15 minutes from a web browser.
Assuming it only takes you 8 hours to do all that, and a decent linux
admin (you) will cost, freelance, up to $100 an hour, that's now $1800 for
your box, which has twice the ongoing rack cost for space....