Again, my comment was more about perception of big stadiums and small stadiums. 80,000 seems to the threshold of large stadiums and puts Iowa in league with OU, Florida, Alabama, Nebby, ND, TAMU, etc.
While there is a larger difference in total seats between 80,000 and 100,000. There is a larger difference in perspective from the schools with 80,000 seats and fewer than 80,000 an more. 80,000 puts you with the big boys.
Take a look at this link to understand what I am talking about. Below 80,000 it drops off dramatically with respect to programs that are considered national powerhouses.
List of American football stadiums by capacity - Wikipedia, the free encyclopedia