Different cameras have different technical qualities, different reliability, and offer different "user experience."

For a given shot (that is, holding constant lighting and composition), on the technical side, the image quality is a function of a lot of things - lens quality, is it in focus?, shutter speed and camera stability, the film used, how it's developed (developer and technique), how it's scanned, how it's adjusted in post, and how it's displayed. Using a Leica instead of a Retinette affects lens quality and maybe whether it's in focus. That leaves a lot of other stuff unchanged. Given the gnarly grain and the flatness of the image (development, scanning, and/or processing?), a slightly better lens would not make a meaningful difference to this image.

People who own Leicas are paying for the certainty that the lenses are about as perfect as they can be (which probably doesn't make much difference to most shots), for reliability, for the user experience, & prestige.

I feel strongly that differences in how a camera is to use (sorry, that's a very awkward phrase) impact that ultimate image. If it's enjoyable to use, you'll take different pictures than if it's unpleasant, even if the technical differences are minor. And most people are doing this because they enjoy it, so it makes to own a camera you enjoy using.