An interesting discussion, on which volumes could be written. The problem is that, after writing volumes, you are not going to solve the debate.
Let us start by defining two terms. “Precision” is, essentially, how many decimal places the scale purports to resolve. (Technically, precision is how small a difference in two masses the scale can detect.) “Accuracy” is how correctly a scale reports a given mass.
Now let us take a very quick look at how scales work. There are basically three designs. A spring scale uses a spring that supposedly will either compress or stretch when a weight is applied to it. Think of the typical bathroom scale. For a bunch of reasons, spring scales are the least accurate and least precise and have no use in reloading. A balance beam scale essentially uses a gradient pointing to the end of a beam to see how two different masses balance tilt the beam off perfectly horizontal. Balance beam scales can be made reasonably accurate by careful use and maintenance, but the readability of the gradient makes precision even at 0.1 grain hard to detect. The modern digital scales use a piezo semi-conductor under the pan, where the semi-conductor changes electrical resistance, effectively converting mass to voltage, which through software is then converted to units of mass. Here is where spending matters: lab grade piezo scales, properly used and maintained – and isolated from outside radio frequency induce inductive voltages – can achieve lab grade accuracy and precision.
For what it is worth, I have a bunch of different scales. One is an older RCBS balance beam that is remarkably consistent, precise to within a couple of tenths of a grain, and accurate to the limits of its precision. I also have a couple of the cheap under $100 digitals. Surprisingly, if used correctly (i.e., run on batteries, not plug in chargers or power supplies, and not proximate to fluorescent lights or inexpensive LED lights), the accuracy and precision of the cheapo digitals equals that of my trusty (and trusted) RCBS balance beam.
Where the cheapos shine is where one is trying to work in bulk measurements, such as sorting brass or slugs for mass. I have no hesitation in using them for that purpose. And since there may be a number of trials and errors setting my powder measure, I will use one of the cheapo to approach the right setting on the powder measure a bit more quickly, though I always confirm the result with my RCBS balance beam.
Bottom line: you can have a lot of fun playing around with different scales, but wasting too much time or money chasing more accuracy and precision than is needed for typical reloading is, yes, a waste of time.
