Definitely not too good to be true. If anything, I'd say the asking price is a bit high. As others have suggested, $150 is closer to reality.

I've got an '89 Rockhopper that came with "Mountain LX" components. That bike looks like it's got the same stuff. "Mountain LX" is related to recent "Deore LX" components in about the same way that I'm related to my great-grandfather.

The 950 was a pretty good frame, a bit nicer than the frame on my Rockhopper, I'd guess. I paid $120 for my Rockhopper, but only because it was in perfect condition.

That's not a bad bike. If you're looking for an old rigid mountain bike, you probably won't do any better.