Of course, spending $10 a pop at the CAT Scales is cheaper than buying your own scale. But there is one distinct advantage to having your own, in that you can weigh the trailer, and tow vehicle, without ever leaving your driveway, before you trust your tires and brakes to a trailer that might be improperly loaded. Driving to the CAT Scales, you have to trust that you got it right until you get to the scales to confirm it.
I don't have one for my Interstate, but if I did I'd need one big enough for duals on my rear wheels. Something to consider if you've got duals on your tow vehicle…
Engineering: Finding complex solutions to simple problems you didn't even know you had.