I agree completely. Relatively small cost difference between 10k and 7k capacity.
By the time you add chain, binders, dirt stuck to the machine, a bunch of shovels, and whatever else to your trailer, you'd chisle away at that residual 900# really quick.
Even still, I personally wouldn't want to load a trailer and routinely tow it loaded to capacity. That's putting all my faith in that guy I don't know that welded it together on a Friday afternoon...or all my faith that those guys in China really DO care how well they manufacture their tires.