It's a legitimate request. People try to haggle everything on Craigslist. I even once settled the deal before meeting the guy and he did not even show up with enough money; he was certain he could hustle me in person. Sure people don't always understand the market price of their goods, but that's not half as slimy as Craigslist hagglers.
Ever notice how some peoples' cars are perpetually for sale? Yeah, I guess it's for sale if you're willing to pay the owner every cent he's got sunk into all the trashy customizations. And labor! Do you have any idea how many hours dude spent hunched over in the AutoZone parking lot? But go ahead, make an offer so he can tell you alllll about this.