Just because you only have 9k miles on the tires doesn't mean you can't either trade them in at the tire dealer, or sell them on craigslist after the tire swap!
I had 20k on my stock tires on our '10-1500 when I upgraded to a set of Cooper A/T3 LRC, still gave me $100 for the set. I know that doesn't seem like a lot, but the same tires were selling for anywhere from $125-200/ set, so since I didn't have to try selling them myself it was a fair deal I thought!
Discount Tire usually has a Memorial Day W/E sale, so maybe look into a set then to save a little more.
The downsaide to the scrap yard scale is it is a little harder to get an accurate weight for each truck axle, and the trailer axles if the ground/ driveway isn't level with the scale (could be wrong, but seems like it could be off a little).
Good luck!