Funny enough my worst experience with selling stuff on Craigslist is the items I've tried to give away for free. I had a nightstand once, it had some damage and I didn't think it was worth anything so I put it on Craigslist for free.

First response I got asked if I had the second nightstand, because it was a pair and it doesn't make sense to have just one nightstand. I did not. They weren't happy about it.

Second response asked if I could deliver it because it wouldn't fit in their car. It's free. No, I'm not delivering it.

Third response complained about the damage and said they would take it if I sanded it and refinished it. I offered to cut the price by 50% (from $0 to $0) to account for the damage, which they were not amused by.

Finally I just put the nightstand on the sidewalk and someone came by and took it away.

I think part of it is what others have said, cheapskates are just worse people to deal with in general. But also I think you run into the issue of people get really suspicious when they're getting a too-good-to-be-true deal and are on the lookout for any sign they might be getting scammed. If they're paying premium, they're willing to let down their guard and wait for the results to prove themselves.

No one wants to drive to your apartment only to find out it's a bait-and-switch or (even worse), that they're going to get mugged.