$100 isn't terrible, but it's missing the center trim disc on the lower knob which is harder to find than the tray.
What's really driven up Craigslist prices on RR's the last couple years has been ebay sales (and ebay asking prices). The nutcase on ebay with an RR-4 is still asking $5900 half a year later. Not a typo..they emailed me trying to cut me a deal for a couple grand off the asking price.
I've also been contacted by buyers of these $150+ ebay machines who were willing to pay that amount to have a working RR when their old one bit the dust and the local dealer tells them 'sorry, can't be fixed'. Too often though, they're buying someone else's problems.