I do the same thing, but I have two different bikes. One is steel, more for relaxed riding, the other is carbon, more of my speedy beater bike.
But anyways, I'd put this bike around $700 tops. For reference, I picked up a one year old C'dale R5000 (full DA10) for $1200, so given that this bike is 4 years old and 9-speed 105/Ult mix I wouldn't spend more than $700.