And yet, they didn't. The items he's selling are still cheaper than they would have been brand new, and he's in effect connecting people with items they want, for cheaper enough for them to afford them, for a relatively small fee.
You ought to rally against real estate agents, brokers, etc. harder than against this guy.
Well, that and managing to ferret out poorly displayed/marketed items and re-post them with better advertising. That is a valuable service, but I'm not sure how much of his activity can be meaningfully characterized as doing so.
Do buyers and sellers go to this man the way people go to real estate agents for their services? What would Craigslist buyers and sellers think of what he does if they knew about it? Respectfully, I think they would strongly prefer he weren't interfering.
Having tried to buy things on Craigslist, nice, clear photos are amazing - it saves me the trouble of shlepping somewhere, looking at the clearly mis-represented item, sighing, and shlepping back home.
As far as the sellers, what exactly are they losing? They stated the price they wanted to sell for, and they got it. You could argue that they could have gotten more with a better camera, some cleaning, and a better ad, but at that point you can argue that nobody should hire ad agencies.
If he's in the business of helping people buy and sell things on Craigslist then he should go to prospective buyers and sellers on that basis. And if he did, he would not make the kind of profit he's making.