The original RTS and RTS II can usually be found at relatively decent prices. The RX can very widely sometimes. My first RX, I paid USD300 for, my second, USD90. The first one broke, which is why the second. I then sold the second one after a year for USD170.
Currently, I have a 139Q. I bought it from a photog in the UK, it was in pretty shape, with a new foam and a new white snakeskin body covering attached, similar to the RTS a few posts above. I paid about USD90 for that one as well.
What has been said about the RX is true, it is a nice rugged camera; the viewfinder is great, the DFI is a nice touch as well. An issue I had with both of mine occurred when trying to rewind re-loadable film cassettes. Sometimes, when I would manually start the rewind procedure, it sounded like it rewound the film, when in fact, it did nothing. I would open the back to find the film still out of the cassette. Using normal cassettes, no problems at all.
At separate times in the past I owned a 139Q, 159MM (which was badly broken and returned), a 167 (again broken but I knew so), and the 2 RX's. I will say, that if you plan on using lenses like the 85 1.4, 35 1.4, or other bigger and longer lenses, the larger bodies provide sturdier grips. Bodies such as the RTS, RTS II with winders attached, the AX, RX, ST and its battery grip, and RTS III, would all be the cameras I would want with the bigger lenses. One combo that I used quite often, though only for a brief time, was the RX with a 60 S-Planar attached.
The 137, 139, 159, ST, RTS and RTS II without grips, and the Aria would all make excellent smaller bodies for use with the 2.8 lenses, which are freaking awesome. I am on the prowl for the 85 2.8 which, if one is lucky, can sometimes be found around USD250. My only wish, is that there was something similar to the Photoequip FM Grip for my 139, the flat front made it awkward as heck to use the 85 1.4 I used to own.
