Ebay can be fickle. On good days, prices are strong for just about anything KF, and on others, well...not so much. I guess it depends upon supply and demand. If two folks want the same item on the same day, then we have an auction.
Right now, literature seems soft. I know at KF meets, most shop and parts manuals trade at a bit less than what yours are listed for. Hydramatic manuals aren't in much demand since most backyard mechanics aren't brave enough to tear into one, however, a regular shop manual will hold it's value because it contains useful info for just about anyone.
Hope this helps!
