Here's my track on the model. Prices rise and fall a bit based on availability. S&W does not manufacture all models all the time.
Smith & Wesson 686 Plus 2-1/2 in barrel Revolver in .357 Mag. Blue Book of Gun Values (37th Edition) indicates between $350 in 95% condition and $615 in 100% condition for this gun. I have 133 recorded prices for this model gun from $350 to $1200 over a period of 12 Yrs 5 Mos ending November 20, 2016. The average price as of that date was $600. No refurbs, no refinishes, regular sights. All represented as 95% or better. No distinction for engineering revision, if any, no special editions, no distinctions for box, papers, tools. Current or last MSRP is $849. The last 11 prices I have for this model since 2/15/2016 range from $360 to $1200 averaging $794