Ron's attachement is cheaper but seems to work the same way; the main difference is mine have an articulated "arm" that allow to put the binding tool away if you want to sew. It`s convenient if you are doing several sewing tasks with the same sewing machine and don't want to screw/unscrew it each time. I must admit I'm very lazy ;-)
The result if very nice; waaaay better of what I can achieve when I'm trying to bind the old fashion way.