Same here, pretty much. It's running 10.8 right now, in fact.
No, I've never really had a job (I'm too young to get a job which would easily pay for this machine, honestly). Actually, we (my mother and I) had saved up enough money to afford it, and I got it for my birthday to replace a frustratingly unstable PC I had built. We don't have a lot of money in general but we had managed to save enough at the time to make it possible.
The plan originally, actually, was to do audio recording/editing with it, although I've never really had the time (I've been very busy with school and stuff). If I ever choose to pursue it in the future, all the pieces are here now to make it easily possible (assuming it doesn't become totally obsolete first (and it probably will)).
I'm willing to live with an obsolescent computer for a few years, although security would probably be a problem (in that case, I'd probably adapt to using some form of Linux). Unfortunately, I have to admit that the 2008 Mac Pro is already bordering on obsolescent (it is the minimum requirement for 10.8, for example; I cannot rely on Apple to support it in the next release or two of OS X, although that is probably likely, at least for 10.9), so its days as a modern computer are probably numbered.
Anyway, I hope I am successfully filling any gaps in your understanding of my thoughts
I'm not perfect, but I'm trying to muddle through.c