I assume you are implying private endeavor with competition.
There was a big stink back when this tool road started about the state granting the Spanish company a monopoly on the route. No new free roads were allowed to be built that might compete, and existing roads were restricted in what maintenance could be done (no widening, e.g.).
The price would not be that high if competition were allowed.
You are correct, and as you noted, even when the project is supposedly “private” there sure seems to be a lot of cronyism involved - like the deal you described to restrict competition.