“Don’t you think brand new multi million dorms, student unions, cafeterias, STEM facilities, exercise facilities and stadiums, fancy theatres, etc are adding to the cost?”
It depends on how they are financed. If the money comes from gifts (so free facilities, probably with naming rights giving to the biggest donor), it will not really add to the total cost. In contrast, if too much debt is used, debt service down the road does have potential to raise total cost and per student tuition.
But, on the other hand, the general phenomenon we have seen is whenever a university initiates a signature project, it generally creates excitement for potential students and brings in more applications. Because university costs are largely fixed (at least for the short term), it actually has potential to bring down unit cost (per student cost) if the enrollment increases.