We have a local free advertising paper back book that comes out every Thursday.
It's called the IWANTA and it's a great local book to buy anything you want.
Some guys have gotten smart and do not put a price on the add nor will they sell on the spot. They will tell you to give them a bid and they will get back with you if you are the highest bidder. I bought a 1972 Bronco about 12-13 years ago and had to give the guy a bid. He called me a week later.
As far as a stupid trade. I guess it doesn't hurt to ask, but to ask twice??
I'd ignore that too.