The problems with this application, however, have already been mentioned, and that is multiple competing overlapping error sources. I might have, say, a .45 Auto case that weighs 3 grains less than another. If that same case happens to have 3 grains too much powder, then the finished cartridge will look perfectly good on a scale but actually be dangerous.
Yes, but if you are a long range rifle shooter and could sort buckets of empty cases by weight without touching one or a pistol shooter that could sort mixed brass into caliber (or better) there is money to be made.
For example the machines that Camdex and Scharch make only sort by diameter and cost over $7000.