How I justify any photographic purchase is how it is going to enable me to get the image I want...
I bought Leica to use for shooting over a thousand rolls of Kodachrome. It made a difference in certain light, not so much in others. It also made certain types of images easier to get and some harder, I saw no difference in using a FM3A or a Leica M6 in shooting street, focusing being faster on the FM3A when the subject was not centered resulting in less "Hang-time" in terms of the camera being at your eye. My professional opinion as to Leica being the best camera for street? Not really, it is up to the photographer, I get great street photos with a Hasselblad for pete's sake…
After Kodachrome was done, i sold most of the really expensive Leica gear, simply did not see the same difference in using it with a month long rental of an M9. A few seconds of adjusting the sliders in post with an image from a D700 or X100 in post, viola, Leica image!
So last year, I re-assembled a lighter kit, M6, M3 along with a 28 CV, 35 F/2 asph, 50 F/2 ZM and a rarely used 90 CV. I also used an FM3A with a 35/2 AIS, all with Tri-X. When I printed the images from the Leica 35/2 and the Nikon one and looked at them with other people, we really saw very little difference in technical terms but saw a fairly significant difference in composition and impact…
Because I could see what I was doing in terms of background versus foreground and focusing subjects off center, 8 times out of 10, the images made with the FM3A and 35 F2 were simply better.
Last week, I sold everything except one M3 and the 50 ZM and put all that wonderful cash into thousands of dollars worth of paper, film and chemistry.
A few years ago, I could justify using more Leica gear, including the 50 asph, not anymore, especially with the prices the way they are and killer cameras like the silent X100. Sure, they are fun to use, feel good, look neato, pretty quiet, but when it comes right down to it, I am a photographer first and the impact of the photograph is essential.
As a professional photographer who's future rests on shooting images with great impact and then selling fine art black and white darkroom prints, in terms of how the photos turn out, I see hardly any reason to justify the new and used prices of Leica gear.
No regrets in buying it for what I needed it for, no regrets in selling it because the job is done and the money is better used for other needs...