These scales work ok in our school setting. Sure there may be a little more flucutation than you would get from a better scale, but a truly good analytical scal that is +-0.1 is way more expensive. We use this scale at Science competitions since a University of Florida professor told us about them at a coach's clinic.
I use this scale and the only problem I have with it is it is not all that sensitive to small amounts. So you put one hop pellet on and it may not register. So you want to add one pellet you sometimes add it and take that plastic piece off then back on to get it to register.
The question I have is how good is a $40 scale you can get from target? These measure to 0.1 grams. Works fine for me.