Some dealers can just... suck.

Fortunately for me, I've never had problems with dealers except for the possible, un-noticed chinse in my dimebag. Buy a scale in my opinion. They're 30 bucks for a descent, long-lasting one. My 30 dollar one goes up to 150 grams to 0.1. That's a pretty good one-time fee for something that's going to save you a LOT in the long run.