wholesale-scales.com has milligram scales for 70 bucks. Liquid measure works fine, right until someone spills it. And don't assume 500mgs is accurate, the RC vendors are bad about being off rather badly in terms of weight, at least weigh on a scale accurate enough weigh a half gram. Or just get the mg scales, it's worth the 70 bucks just to be able to bitch at your weed dealer that the last quarter weighed 6.927 grams.