Looking for the cheapest solution to fit my needs.

I would really like to get a 3d scanner setup. I have seen a couple used pro units go for a reasonable price but still a mighty big stretch for me.
I have heard things like David and Scenect are not very accurate but I cant find much on actual accuracy.
I would be very interested in making my own setup if I can find something that will work. Are there any good software options other than David that work with a slit laser/camera style scanner?

Can anyone get me a rough idea of accuracy with a homeade scanner and David or other software? How about say Scenect and a Carmine 1.09?

Are there any other cheap DIY options?

What other options new, used or DIY might there be under $1000?
I really need at least .5mm accuracy but I would like much tighter than that if possible.