It has been my experience that RB are more sought after than SB and a 3" barrel on an airweight takes away from the purpose of an airweight. Blue Books lists at $250 @ 95% and $400 NIB
I would say around $350 for this model in nickel. I purchased the same pistol in a blue finish last year, no box, and paid $325.
Not as many nickel versions were made. it is mentioned that of the total production of most models in each year, about 10% of those made would have been with a nickel finish.