If you go on eBay and look up "sold" listings, you can find quite a range on actual sales prices. These sold price ranges do not include shipping. Condition was not the only reason some listings sold for more, but it is a major factor in my opinion. You could probably get close to the higher end of most of these ranges if you had these on eBay as a fixed price listing, had an attractive layout with nice photos and were very, very patient.
D&D - Empires of the Shining Sea $20 - $40
D&D - The Ruins of Myth Drannor - $20-$50
D&D - Return to the Tomb of Horrors $25 - $60
D&D - Tales of the Lance - $20-$40
METAL Miniature - Takhisis - Queen of Darkness - open but complete $100-$200
Truth is worth finding and life is too short to work for money.