Here are my wild guesses (because I don't track sales or use eBay as a model for value):
Wilderlands of High Fantasy boxed set -- $65 - 120
Player's Guide to Wilderlands -- $30 - 50
Caverns of Thracia -- $15 - 25 (assuming this is the
d20 version)
City State of the Imperial Overlord -- $40 - 60
CZ: Yggsburgh -- $5 - 15
CZ: Upper Works -- $125 - 200
Tomb of Abyssthor (sp?) -- $10 - 25
DCC 35 -- $20 - 45
RAR -- $125 - 200
Ptolus -- $125 - 200 (assuming this is the complete version with all extras)
Iron Kingdoms books, incl. Witchfire Trilogy Hbk -- $50 - 100
Possibly The Drow War HBks, esp. book 1 -- $30 - 50
Those who can, don't. Those who should not, do.