I think the real value is in its ride. It's a mass produced frame, and was Bridgestone's second tier road model, but it's a surprisingly lively ride. I gave up an '88 (paint was in sad shape, and components weren't original - not upgrades either really), and I'm sorry I did. I sold it for $250 a couple years ago (I had completely overhauled it, so it was ride ready).
I'd estimate $200-$400, maybe a little more if someone absolutely must have it. All original in great condition will help, as there are Bridgestone fanatics out there, but the components are really nothing special, and the RB-2 is not as coveted as the RB-1, despite a similar ride quality.
http://sheldonbrown.com/bridgestone/1991/index.htm
http://sheldonbrown.com/bridgestone/...ynergy1990.pdf
http://sheldonbrown.com/bridgestone/...oneRB21992.pdf