8 euros is the price of an incomplete cable. Like you i've dozens, then i found some UK guys that do the bad work for me
In order not to appear like a crook, let me add that my customer standard do not speak/read english because he's 40-50 years old and is not very computer capable.
In that price ofr 129 euros, there's a good part of online support to help them dealing with that freeware.
Another part is knowledge about air suspension. As an example, if you get height sensor incorrect, it's not because your height sensor is dead.
I can't reveal you how they find my shop but google works fine.
PS : Sorry for "truck", too much time on US bulletin boards