I'm curious, did you weigh the buds with the bags on the scale, and not calibrate the weight of the bag? Because it would sound about right that a small ziplock with the seal would weigh about 1.8 grams. A sandwich baggie tends to be .9 or a gram. I know because I've weighed all kinds of bags.

If you;re in the Uk, be aware of the sand and glass crisis you are facing right now.

Not trying to be a dink, but that would be pretty careless on the dealers part.