I mean actual colo space, like you just pay for 4u, 8u, bandwidth and power. No machines, just space.
Both are "cheap" just along different axis.
Right, that's the same thing I was talking about. But again, how is paying for 4u/8u of space at all "cheap", when all you want to stick in it is your own 1u junk server?
I'm not sure you have the same definition of "cheap" as I do. $5/mo for a 1GB DigitalOcean droplet is cheap.
Buying old-but-badass hardware seems to be similarly cost-effective for that purpose (if that link is to be believed), but where (other than "a friend in ops") can you get 1U/2U of colo hosting for anywhere near that price?
I guess, if you're talking about the marginal price of an extra 1U/2U on top of your existing production rack, it can be negligible. For non-business-affiliated goofing-around, though?