I have just finished installing brakes on our 2015 standard 13" Scamp which we bought new without brakes. The job was pretty much straight forward to do. Remove the old hubs, mount the new backing plates, and install the new hub/drum assemblies. At this point I adjusted the new brakes. The biggest "figuring out" part was how to run the wiring. Our Scamp has no bath so all the wiring comes into and through the front storage compartments. I ran two wires (brake power and ground) inside the front compartments around on the drivers side following the factory wiring harness. I Drilled a small hole through the floor in front of the drivers side wheel well, ran the wires down through the hole and connected them to the brake assemblies.
The cost of the job was about $450:00 which included the controller mounted in the TV. Scamp charges $275:00 when brakes are ordered as an option on a new trailer and the cost of the controller would be added to that. But still not cost affective to install the brakes after purchase. Also there is no labor charge in that $450:00 as I did the work myself.
I have two non-brake hubs if any one would want them. Your cost would be shipping from mid-coast Maine.
Scamp and other manufacturers get their parts and accessories for a pretty good discount. Scamp usually charges for options about the same price as we (customers) can buy the parts for. Like you found out if you want an option you are usually better off just ordering it when you order the trailer. I have a brand new Scamp furnace in my garage, If I were ordering a new Scamp I would order it with a new furnace installed instead of installing the one I have.
With axles and brakes, If you decide you want brakes and your axle is 10 years old you are really better off just ordering a new axle with brakes installed.
Eddie