One real difference is that somebody with the right skills and a few thousands worth of tools can rebuild just about every part of a mechanical camera - given a vise, a small lathe, a drill press, polishing machine and a set of screwdrivers, files, saws and pliers, and arbitrary amounts of time, I could rebuild a Leica M3 from scratch (i.e. bare blocks of metal and glass). It might cost me fifty times as much as buying one used, but it is essentially possible.
Electronic devices on the other hand tend to be irreproducible (and unrepairable) the very moment the last components have vanished from the surplus market, as it is plain impossible to re-build a IC or sensor chip at artisan level. As the whole tool chain has moved on, not even a industrial scale recreation of a past IC is possible without turning back time on a bigger scale, as the tool industry would have to get back to building lower resolution steppers, now prohibited chemicals would have to be legalized and reintroduced etc. etc.