I have an old RCBS Chargemaster scale, and as an experiment, I bought two cheap milligram digital scales from Amazon to compare it to.
The first scale I bought.
This one reads to 0.1 grains. The drift was really bad, and the drift was much more erratic than the drift on the Chargemaster when setup next to each other. I just use it to check bullet weights now.
The second scale I bought.
This one reads to 0.01 grains. The drift on this matches the drift on the RCBS Chargemaster scale. It is more sensitive than the Chargemaster in that I can remove one kernel of powder, and it will show the difference, where the Chargemaster reading may not change for one kernel within it's internal rounding limit.
If I trickle 40.1 grains on the Chargemaster, then weight that powder on the cheapo scale, it may show 40.17. I then remove one kernel, and it goes to 40.11, with no change on the Chargemaster. So the resolution is a bit finer.
The Chargemaster and this cheapo drift in unison with change in temperature. The several times I've used them together, they drift almost identically.
I use both at the same time - trickle onto the Chargemaster, then verify on the cheapo scale if I need to remove one or two kernels.
From my results, I can use this scale as a backup should my Chargemaster die, until I get a new scale. I'm happy to use it for comparison, but not as a permanent replacement to the Chargemaster scale.
My next experiment is to try a more expensive analytical balance in the $130 range.