John,
I know you didn't ask about this, but for what it's worth, you can get your unit weighed for a lot less at other places. All gravel/concrete suppliers have scales, as do all farm feed stores. I'll bet that you can find one near you.
I have never been charged at all to weigh each axle on my truck/trailer combination at our local feed store. They always ask if I need a slip, or just want the weight. I have always just asked for the weight. I guess that they might have charged me if I needed a piece of paper.
Happy hunting.
Loren