It's going to depend upon where you are, how many of them are in circulation in your area, whether the electrical components are all sound and safe to use, presence and condition of attachments and accessories, desirability of that particular cabinet, etc.
That said, I do tend to lose my head over good 15's. I've refurbed 4 of them now and I just love the darn things. Two of them I've given away, but one of them gets used almost daily for piecing and/or quilting or garment/home dec construction.
They're wonderful sewing machines.