I think, in general, that good FSU gear is definitely going up in price. I've only been serious about FSU stuff for the last 5 years or so, but I've been an avid "accumulator" of photo gear for at least 30 years. I remember when FSU was considered cheap (price and quality) and we looked down on it as the source of all those gawdy Leica fakes. The awful fakes are still around and even those are commanding real money these days!
Truth is: There's nice FSU cameras and lenses. I'm among the surprised. There's junk too. Educate yourself and you'll be nothing but happy.
CV wide angle lenses work fine on FSU bodies. I use a 21/4 and 35/2.5 on my Zorki C, Fed 3, Zorki 6, and Fed 1 with great results (to me at least). Conversely, I also use the J-12 on Leica screwmount, CV Bessa, Canon screwmount, and Leica M. Works quite nice. I like the results I get with the CV 35/2.5 more, but its purely a matter of personal taste. Someone said it above; You generally need to avoid focus cams that aren't circular (and wide helps too). The incompatibilities you read about on the web are mostly unimportant. wolves described one of them, there are some other issues too. These issues vary with time period, manufacturer, and type of equipment. In general, really old FSU will present some problems, really new stuff will not, but overall quality of build tends to be lower. Now, to confuse things, some older lenses are definitely better and more desirable, while the newer versions not so much. Actually its all fun stuff to learn about. Educate yourself and you'll be happier.
I would avoid the "optical blocks" offered on the bay. Not worth your time and not practical. Yeah, the Kiev/Contax versions of J-12 are out there for cheap and the LTM versions keep going up in price. Frustrating, but its an indication of how nice an LTM J-12 can be, and how many people are discovering that. I'm aware that unless you can find a sane source for these things, the going price really is $100, even more. I think Fedka.com (an honest, reliable business with excellent customer service) wants well over $100 for J-12s. I occasionally see them here on RFF for around $80. If one comes up, grab it without thinking twice. First of all, it will be a reasonable price, second of all, it will come from an RFF member (I guess check to make sure) who typically will know if the lens is a good one or a dog. I trust these folks to know what they're talking about. Really early J-12s are desirable because they often have genuine Zeiss optical (and other) elements. Some really early lenses are fully Zeiss that were just assembled in the Soviet Union. Some people think that the later lenses (e.g., the black lenses) are lower quality, but then some people think they're better (except for the real early ZK I mentioned). I find that you just need to get a lens that isn't beat up on the glass. I have a 70's era black J-12 that's great. I have a 60's era chrome that's great. They both have unmarked, clear glass. What I'm saying is, just get one in good condition. If you can get an accompanying viewfinder, that would be especially nice. You might think you can get by without it and guesstimate 35 coverage, but its so much nicer to have the viewfinder. Funny thing is I don't have the FSU viewfinder, but rather the CV version. I love that one. I'm told the FSU viewfinder is perfectly nice. Try to get it.
Avoid the Orion or the Russar. Way overpriced for dismal specs. CV, Canon, Komura, etc. will be a better pursuit. And don't hesitate to pick up a nice Fed 2 or Zorki C (S). For me, those are probably the best bang for the buck among FSU bodies. Welcome aboard...
