you can build one for about 200-250 or so , use drawer slides, hobby cnc board, HP laserjet stepper motors (can get them free or dirt cheap from copier/printer repair place. i even have 5 extra from when i got mine i got 3 for 15 dollars. I might use in another machine.
then just build it out of wood/mdf and use an old computer you may have.
then a dremel and your all set.
Heres an example of what can be done.
http://www.cnczone.com/gallery/showp.../cat/500/page/