Craigslist is the definition of a buyer's market. There's typically enough of any given thing there to keep prices low and even if there isn't people aren't willing to spend much so they'll wait you out. I've low balled people on Craigslist jokingly and had them contact me days later saying they'd accept the offer.Buy on Craigslist, sell on eBay.
That's always been my strategy. As long as you have nice looking stuff, you will always make a profit on eBay even after the 13% they take with eBay and PayPal fees.
I've bought several laptops (especially macbooks) at dirt cheap prices and sold on eBay for quick flips. I am more about speed than anything else, so trying to squeeze the most profit off each item will exhaust anyone.
Put up a hot in-demand product or car and maybe you get fair value for it but put up let's say a high end 4K TV that's worth $2000 and you wouldn't even get $500 for it. On eBay you'd probably get closer to $1200.