returning to OP's question.......
I looked on Craig's List this morning. Lotsa Weber grills offered. Lotsa variation in price and condition. It seemed to vary from a fairly new grill in nice, clean condition at a bargain price to a POS that needed burners, flavorizer bars, grills and paint for nearly new price. So, no consistent evidence there. If you want to get your Weber sold and out of the way, price it at what you would consider a bargain and if it doesn't move very quickly reduce that price. It's not worth the effort of a full blown sales campaign for an extra $25 - $50.
Note: Craig's List in Chicago is near useless. Popular items at reasonable prices are always sold quickly, usually before you can make contact with the vendor unless you sit looking for things to pop up all day. Most stuff is dramatically overpriced and often sold by vendors that picked it up at a garage sale, etc., and can't tell you if it works now or ever did. I've sold lots of stuff on Craig's List but almost always good stuff that I price low and it's generally gone within hours (or I move it to the "free" section). If it's crap, I just put it in the garbage.