Thank you all for the feedback.
So $1000ish is not unreasonable. I remember an Ebay auction a few years back where a
SW copy went for $1000 but it was determined after the fact that the booklet was not unopened. That ending bid was the only recent valuation I remember to give me even a ballpark figure.
The buyer is still deciding on whether to purchase this module and some of my other character sheet sets because of the value. Unfortunately, I don't have any more ultra-rare, ultra expensive modules (although I do have some complete character pads, 1977 wizard logo) and a few other character sheet sets complete and in the
SW. Since he has been a loyal buyer, I will give him time to decide but if he declines, I will sell it to an interested member.
I will upload some more images if anyone is interested.