If you monitor Craigslist closely, you can score good deals. My purchase was legitimate. Think of it this way, the good deals are quickly removed from Craigslist while the over-priced ones remain. When I want a piece of tech, I use Page Monitor in Google Chrome to check every 5 min for new listings and am the first to jump on any. Regarding safety when purchasing - always meet in a busy public place, preferably with video surveillance, bring WiFi hotspot, check serial numbers on Apple website, open all packaging and activate Apple device, verify condition - and THEN pay the money. Apple warranty is so good thought that as long as the device shows as being under warranty on Apple's website, and there is no sign of abuse or water damage, you should be fine.
When the iPad 1 came out, I would buy them from people and then turn around and sell them the same day for as much as $200 more. Not everyone is savvy, and MANY people are feeling a financial squeeze and need to sell fast - OR maybe mom bought the device for them and they want to sell it to pay for their apartment they secretly live in with their girlfriend (this was one of my favorites).
No to mention, many people can be talked down in price pretty fast on Craigslist. The bottom line is that the indications of value from list prices mean very little. We can ask whatever we want, after all.