Digital weight scales are popular, just that you need to level them and sometimes use something so the points or arrows won't wander around or roll off. Some nice ones only go up to 500 grains and anything over and left on could ruin it.
I usually use my Homac magnetic balanced scale. And the one pictured rarely. It is accurate, but only as I noted. If not the reading will be off slightly, but consistent enough to say points or arrows weigh the same.
$20.00 when I bought it. Weigh Max, model BX-500. Gives grains, grams, ounces, dwt.