Whatever their cost base, they're going to charge us consumers the maximum they can get away with. So increasing the spectrum price doesn't change what we pay.
Err... I am not so sure about the logical relation between these statements.
When there is competition, every player wants to cover costs plus get as much profit as they can without losing their customers to competition. When the cost base is the same for all competitors, they all end up adding some "average" profit margin on top, and this results in the "average market price" that the consumers pay.
When cost rises for all the competitors, they all do the only possible thing, and raise prices simultaneously, preserving the margin. If any of them don't, it starts losing money and go out of business. If any of them rises prices too high, it loses customers and go out of business.
In a sense, auction on "natural resource" is anticompetitive, because it raises the barrier of entry, while doing nothing to impose "fairness".