I cannot see the rationale behind the cost increase this patch introduced.
the intention of this patch as a whole is to simulate the combined material and personal effort for maintenance of infrastructure. the intention of the non-linear scaling in particular is to simulate the management overhead. the bigger your company, the higher the amount of money you have to spend on management personal and technology (e.g. signalling, scheduling, ...) in relation to the money you have to spend on doing actual work (driving, repairing, ...)
e.g: say for simplicity you have 1 person in charge for 1 tile of rail, and for any 2 persons you need one manager to coordinate the work of these people.
- for 1 tile you only need 1 worker (=1)
- for 2 tiles you need 2 workers, and 1 manager (=3)
- for 4 tiles you need 4 workers, 2 managers, and 1 manager-manager (=7)
- for 8 tiles you need 8 workers, 4 managers, 2 manager-managers and one manager-manager-manager (=15)
you see that you now need 2n-1 people for working n tiles. this is only a linear factor in number of personel, but each level of managers has a higher wage than the level below them, which makes the personel cost non-linear.
Although I can see your point, this interpretation leads to hundreds of management layers in a reasonable sized company and as such hardly serves as a realistic rationale. Again, I'm not suggesting realism above all else, but this might be one of the cases where a more realistic approach might be appropriate.
the effect of "labour unions" etc. is roughly covered with inflation, which is an entirely different topic.
There are many differences. For starters, inflation does not react to your profit and/or network sizes. In a way it actually promotes early infrastructure spamming because it is applied to construction costs as well, so better build that long railway now while your money is still worth something. This is pretty much the opposite of what you're trying to achieve, although it is obviously diminished by maintenance costs.
My idea of labor unions directly reacts
to a company's profit and network sizes, which, unless I completely missed the point to begin with, is exactly what this is all about. It promotes usage of the different transportation methods in a transparent way, i.e. a monolithic train company will have serious maintenance costs due to their mighty train labor union, and thus be less profitable than a balanced one.
Note that I am not suggesting the implementation of actual personnel numerical values, they much rather derive directly from the size of the infrastructure, which is already grouped into what I would interpret as labor union.