Security Six prices are strange right now, I just got a low-back in holster worn but hardly fired condition for less than $400, but then again I have seen holster worn stainless steel later model 4" Security Sixes go for almost $600 on Gunbroker. It depends on who's selling, who wants it and just a lot of random factors.
A beat up but functional $350 Security Six wouldn't last 10 minutes at a NE PA gun show, but I have seen decent Sixes relist for less than $400 on GunBroker.
Luckily for me I sucked up every holster beat, thrashed looking Service Six for below $300 I could find over the past 4 years and now I have enough "shooter grade" Sixes for life.......buying the used Rugers is the cheap and easy part, now finding enough ammo to shoot them is the challenge