Hello Baldeagle,
Wow, 2-3 Dollars each!. That would be at least over 300 Dollars for a D.VII fuselage (60 turnbuckles two ferrules at each...). I could do them on the lathe at 50 Cents each and with my wrapping tool above at 75 Cents each. The same goes for the Fokker securing pins made from spring steel!
For those of you who are not quite clear what we are talking about here see the image below. These are the securing ferrules of our Fokker triplane having 5 turns:
The control cables of Fokkers aeroplanes consisted of steel cables with a hemp soul. The rope itself had a diameter of 4 mm and was from six braids each which were turned around the hemp soul in the middle. These cables are very flexible. The ends were spliced on a length of 50 mm. At these locations the control cables have been wrapped with thin steel wire which was secured by running through the splices at its end. I also have seen at other manufacturers of this time that the ends were soldered. This did not stay at the place of Fokker for me yet. We will not do it at our aircraft either since the heat is a unnecessary strain on the material anyway.
It might be of interest here to mention that the cables spliced ready were stretched with a load of 500 kg. We have done it that way on our previous triplanes - and by the way, we can offer this service, too!
As far as it concernes the ridging wires, here I can only talk about the underccarriage bracings of the Fokker D.VII. These are made from 6mm steel wires without the hemp soul. Its ends are spliced, too. At the top the ends are spliced directly around the fuselage structure while the bottom ends are spliced to the turnbuckles.
Best
Achim