Craigslist wouldn't be much different from most advertising venues. A few years ago I sold my wife's year old Giant OCR1 with maybe 300 miles on it for $600 (Al, Shimano 105, like-new condition; good starter road bike, but wrong size for wife). You couldn't touch that bike new for less than $1100 or so, definitely a good deal if that's what a prospective buyer was seeking.