I guess I've looked in all the same places as you and found very few copies of either title. All priced around £20.

This does not mean to say they are scarce and sought-after. Probably just scarce.

My experience with these types of oddball is not good. A good title with plenty of keywords is essential, as there may only be one buyer out there.

If they cost you nothing, I would list at a fiver, but don't persist if they dont attract any attention first time round.