You can throw a bunch of boxes in a closet and it'll work. A surprisingly large amount of the early Internet was "a spare box under my desk."

The problems start when they become part of your critical path and you're on vacation and nobody knows WTF is happening.

I mean, it's a risk. If you're OK with that risk then go for it.

It's really about the politics of your office.

If everyone is OK with the idea that the box is in some closet somewhere that's fine. I've been part of a bunch of startups where we were running infrastructure on spare hardware. Sure it's not HA, but we didn't need it...or it was at least HA enough for what we needed.

But if you can motivate that same sysadmin to spend his skills on something more directly benefiting your company, then you should still buy it in.

And I think in most cases companies want to focus their employees and efforts on their core business, and if that doesn't include setting up and maintaining hardware in the long-term, then you don't build, you buy.