The RB-1 is a nice bike. RB-1 fans keep the market value up there, and there's nothing wrong with that.
As a functional good steel road bike, there are bikes as good, IMHO, at $250, like some Fuji, Panasonic, Centurion, or Nishiki models, if they have better components. I put the GPX squarely between 105 and 600, and I've had identical Tange 1 frames sporting each group, all at the same time, so I figure I can relate.
A clean RB-1 with an upgrade to tricolor 600 STI package, now that's a bike that can stomp a lot of newer stuff costing twice as much, if not more. Figure what you pay for the upgrade, less the offset, and you've got a $400-$500 bike that'll rock.