Here is a site that lists scarcity and values of vintage D & D modules, books and boxed sets. Most are common and can be found of eBay regularly for $5-$20, even the non-first printings of the original core books from the late 70s and early 80s. Most of the 1st printings of the books or rule-sets can be valuable as you would expect. There is an early version of the Deities & Demigods book that has stats for the H.P. Lovecraft Cthulhu mythos. TSR used that stuff without permission and were forced to remove them from subsequent printings. That book is worth probably 10 times a regular version.
Dungeons and Dragons Scarcity and Value
Hey, I have that version! Got it brand new back in the day for Christmas.
That is cool Shadow it's neat to be an original owner of that book. I picked one up about 15 years ago in a used book store for about 10 bucks.