The difference in price is due to the interface capabilities. LT still lets the user work in and with 3D.
If you do program in VB and want some CAD capability that is not quite so expensive, you could look at VectorDraw. It is a component for VisuaBASIC that gives the programmer some control...
I haven't looked here for your particular answer, but you might want to try this site:
http://www.genoadesign.com/link.html
They have several free blocks available for download. You might also want to look for some of the international sites that do the same.