Though Ebay is a little nuts these days, you can always look there to see what things are currently going for, for comparison. Depends a lot on its condition. They are not usually as expensive as a Golden Edge.
Depends on condition and size. A square point in restorable condition is worth about $60 to me. Although they fetch ridiculous prices on ebay some times, I think $140 on one in good condition is fair. They are excellent shavers and no longer in production. A new razor of similar quality will cost you that or much more and to me the DD razors had some of the best steel around. The really ridiculous priced DD's are the Grim Reapers and the stainless. Those are really expensive and fetch huge prices in even horrible condition.
I would not get too hung up on getting a Dubl Duck, just like i would not get too hung up on a Fat Boy, Red Tip, Ferrari, Mc Mansion by the sea, etc.... There are plenty of razors out there that shave great fro a fraction of the price. I will take my Torrey over my Dubl Duck any day of the week.
Thanks for the links I was just wondering saw one for 20 on craigs list but it was gone. I have a duck gold edge tried to shave with it 17 years ago going to send it off to glen have it honed and use it now that i can read this fourm and learn. and yes i bought into the name fat boy tired of useing borrowed form bro. I will be thrifty untill i hit some OT at work. Thanks for all the repilies B