Its people thinking they can always get favors. Its the self centered attitude of the days. I've started to list my classifieds for slightly higher than what I'm looking for because in the end EVERY single offer I get is lower and I'm just looking for a quick sale.
Same person who offered me $4K wanted me to drive 4 hours to THEM for them to look at it. Same person called me again and offered $4100 because I was uninterested in selling. Same person called me 4 times in the matter of 10minutes because I wasnt answering.
its not favors, its just this crazy bargain thought process of most of the people that use CL. It's go as low as possible, thinking that people that list on there are in need of crack money. I do the same exact thing as you do - listing much higher - because I always can expect low ball offers, most of them, extremely low.
Sold my motorcycle on there after about 2mos. I believe I had it listed at $5500... I had a guy offer me $3200, because he "worked at a car dealer" and that was the "trade-in" value. I told him I wasn't fucking trading in. I later sold it for $4800 (which was very good actually).
Tires... omg.... I've had high performance tires on there, set of 4 for like $600. People start sending emails, "would you take $200?" - NO, I'm not starving for food right now or eating ketchup on a saltine, wtf?! or the best is, "well, I can get XXXX brand/chinese cheap shit tires for $89 each" - that's great, go buy them. I don't know what it is, but its become a "culture" of just lowballing as much as possible. Sometimes it works I guess.