For cheap 3D software, check out MeshCam at
http://www.robgrz.com
It's in beta right now, but it seems to work pretty good. The final price is supposed to be about $100, but the free beta has no expiration. It will create 3D gcode from just a bitmap, or from an .stl file which you can export from AutoCAD (solid models only).
A lot of guys in the homemade wood router section, like Eric said, build machines for around $1000, some more, some less.
Gerry