If your question isn't facetious, the reason not to spend $3500 on an analytical balance is simple...you won't be able to shoot the difference. In fact, I own and use a very high end Mettler-Toledo balance that has two weight ranges, one with readability to 0.1mg and a maximum load of 200g, the other with readability to 0.01mg and 40g load limit. I was very lucky to get it for free, otherwise I wouldn't be using such a balance. I use the 0.1mg/200g setting when weighing powder. If you estimate the effect of +/- 0.1mg on velocity for charge weights in the 20gr to 40gr range (or higher), it is negligble. We're talking about a small fraction of one foot per second velocity. The average chronograph can't even come close to measuring velocity changes that small, and you certainly can't shoot the difference. It's simply never going to be the limiting source of error in your load ES/SD values. If I ever have to buy a comparable replacement, I will most likely go with the Sartorius Entris 64, which has comparable tolerances and features, but costs thousands less.
A single kernel of Varget has an average weight of ~1.4mg, so a balance with readability of 0.1mg and accuracy in the ~0.2mg range is more than adequate. If you try using the more sensitive range (i.e. 0.01mg), the balance readings will be jumping all over the place from air currents, or your body movements, unless you're also willing to purchase an expensive vibration-dampening table to put it on, along with replacement nitrogen cylinders in order to use the table. It's simply not worth it for a difference in powder weight measurement you can't even shoot.