Rick,
You can buy them as a kit to assemble I think, but I bought it as a set of castings and machined them. The casting set was £63 I think, but to be honest, by the time I bought all the tools I needed it was prob about £150.
I already had a small lathe etc. The machining was a little challenging, working out how to set up. It involved a little lateral thinking. For one operation I held the workpeice in the lathe chuck, and mounted a dremel flexi shaft in the cross slide clamp and used it as a mill. It worked!
Ian