I don't see camera gear as an "investment." I have a pretty nice little collection containing pre-Civil War lenses, some really nice "big name" cameras from the 1930s, a 1940s Leica IIIc and three lenses, and a nice selection of LF lenses vintage 1895--1930. These are toys, not investments. At best I just expect to break about even when I resell.
Kent in SD