It's not uncommon. But remember that these are asking prices, not selling prices, and craigslist is a place where people negotiate. The retailer, by contrast, always expects to get its asking prices and avoids the whole negotiation phase.
I've seen lots of people offering "new in box" tools at double the sale prices from the previous weekend, as if they were making a living buying up ten $49 weed-whackers and then selling them online for an even $100. Places like harbor freight have made Chinese-made tools so remarkably cheap that many American buyers haven't yet adjusted their price expectations, and a ruthless seller can exploit that information asymmetry for profit.
And then some people just legitimately prefer to buy from CL over retail outlets for weird reasons, like a specific social anxiety disorder where they can't deal with crowds, or a hatred of big box stores, or an inability to drive there and get it themselves. Those folks are sometimes willing to pay a very hefty premium to have someone meet them locally with the item they desire.