You have a nice coach! I don't think I'd want to cut corners on that to save a few dollars! Mine are pretty low budget builds by comparison. I'm installing used parts and making them fit because I have to.
I still think the installation quote is high, because you are just running air lines, installing a switch, and maybe replacing a u bolt with a longer one.
Here are a couple of pictures from one of my trucks. The school bus suspension setup is different than a class 8 truck so I wasn't able to use the brackets that came with the chains because the width of the U-bolt was longer than the entire bracket. If you ordered chains built for your axle and suspension they would have brackets that would bolt right onto your axle.
You can see in the pictures that I had to build the red primer colored brackets. If you look closely you'll also notice that the U-bolt isn't long enough because there should be threads showing below the nut. Before it hits the road it I'll have to replace them with longer ones.
Some of the original brackets had two holes in them, one for each end of a single u bolt. The others had three holes, (two for one u-bolt and one for a single end of the other u-bolt.) I felt it was strong enough to just use two holes.
Another thing that I did was run a 1/4 inch air line to one and a 3/8 line to the other (from the Tee) I did this so one chain would deploy more quickly than the other preventing them from meeting in the middle and binding. I'm not sure how the manufacturers deal with this or if it's even an issue when you're running down the road but mine would hit each other during mockup and testing.