FSU stuff was more common in RFF classifieds some years ago. It still shows up sporadically, and usually it's items that are in good shape, or known performers. That's a good thing. I still like FSU gear; it mingles with my high-brow gear just fine.
I expect J-12's and J-3's to continue making an appearance. Also bodies in good working order. In the past few years I bought a NDVK Fed 1 here, also a nice J-3 that was shimmed for Leica (thanks Jan), a good J-12, Zorki-6, and a few other bits I can't remember. The rest of my FSU came from elsewhere. Back when the Bay had decent gear I got a Zorki-C and a Fed-3 that were in perfect working order from day one (and still are). I don't think that happens anymore.
As for items less than $100, isn't there a specific category for such items in RFF classifieds? Perhaps the ad fee for this category is lower?