Here is the real meaning of "Feeler":
Hey! I really wanna sell this item because I don't want it anymore (which is why I am posting in the classifieds), but I don't want you to know how badly I really wanna sell it. I want you to think that I am really stressed out about letting this item go, and I want you to fear that I just might keep it, and that you will be extremely lucky if I decide to sell it to you, therefore you will hopefully be inclined to give me lots of money for it. But I will only sell it to you if I can get more money from you than the item is really worth. Hence my "feeler" ad......to see if I can be successful in me coming out ahead in the deal. If I can't, then I won't sell it.
Nothing like brutal honesty, eh?