This, too, will change. Keep in mind the market is a fluid animal.

Up until about five years ago, I had a steady stream of old road bikes, because no one wanted them. I could buy all of them I wanted, some pretty nice, always under fifty bucks, and sometimes under five. No one else wanted them. I would buy old Fujis for five bucks and help a VCU student convert them to fixed gear. Good luck with that now. I would pass on five dollar bikes that today would sell on the local CL for two hundred bucks, I didn't see the use at the time. Once I gave away about twenty frames in a giant house clearing.

Another time I bought an old Schwinn at an auction for five bucks, removed the brooks saddle and tossed it back into the auction pile sans seat. People at that auction thought I was crazy for years and years, because there was no resale value on an old ten speed. None.

Eventually, the market will move and shift, and those unsalable MTBs will be worth something, and considerably easier to sell. I recall passing on dozens of mixtes, plenty of Japanese bikes, lots of low end cottered crank stuff from the boom years, any and all of which I could have had for a fiver. At the time they were unsalable. Any road bike-- anything, even a 531 framed one-- would just sit in the local thrifts. Today, they're gone as soon as they are put out. There's a variety of reasons. One is the number of them showing up at the local thrifts has declined drastically.

Oddly, I haven't particualarly suffered; I don't find as much stuff, but the stuff I find is way, way nicer on average. Go figure.

But the market will move on MTBs one day. When? You'll have to figure that out.