Very interesting thread! As a complete amateur, I wanted to chime in on my thoughts. I have four analog cameras I routinely use: a Pentax K1000, a Canon A-1, a Canon F1, and a Nikon F6.
Strangely enough, I think the Pentax and the F1 are my favorites. I will admit that I usually get better results from the Nikon, but the Pentax and F1 are more fun and more fulfilling when the results turn out the way I'd hoped.
The Nikon is a much more expensive camera, but I do get better results with it: the metering is better and the lens is better. Does it enhance the composition or aesthetic merit of my photograpy? Not a chance. But it does help the technical aspects and is helping me learn to improve my photography with the manual cameras.
As far as justifying the expense, my thought was that the F6 would serve me well as I learned more and would be a camera that would not become obsolete as I continued to learn more. One often spends more in the course of upgrading from product to product to product than if he has simply bought the more expensive product at the outset.
I think of it like my guitar playing. When I first began, the quality of a vintage Martin D-28 would not have been of any more benefit to me than a well setup $300 starter guitar. As my playing developed and improved, the subtle precision and tonal qualities of a vintage D-28 elevated my playing beyond the limits of the starter guitar; but I had to reach the level of proficiency at which those differences became critical, otherwise those differences would have been lost on me.
My dream cameras would be a Leica M3 and a Hasselblad (I love the mechanical precision and sharpness of both and the square format of the Hasselblad), but I recognize I haven't reached the level of proficiency at which the subtle differences will elevate my photography beyond the equipment I have. Right now, I'm at the photography equivalent of a using a new Martin D-28: they're great for moderate and advanced players and will serve a professional well (meaning, the Nikon F6 will serve me as a growing amateur well into the future). I hope someday to be the kind of photographer that would benefit from the vintage D-28: tonal colorations and construction matter to a skilled artist (meaning I'd love to be at the level where those nuances of a Leica and Hasselblad aren't lost on me).