I have a Harbor Freight one, it is within about 1/2 ounce. How do I know. I balance as perfect as I can. Then take wheel off and remount. Then I re-balance, taping the weights in place. Doing this several times, I never have needed over about 1/4 oz to rebalance.
I have tested the tires to 120 and no vibration. Beemer likes that, ran a LOT smoother for a while. Good enough for me.