season attendances are missing the ROC addition to the numbers. BYU's first 3 home games this season had attendance of 2000, 2600, and 2200 all before BYU started classes. But even ignoring the student seating, these 3 early season games are still not sellouts in the general seating area. BYU even opened against a top 25 opponent St. Louis but had lowest attendance of year for that one.
However, for a certain number of later season matches once BYU had the huge momentum and had beat UCLA and there was excitement about big 12 and then especially for home NCAA tournament games they could have fit much more than the 4100 capacity they had.
Unfortunately, stadiums don't make much economic sense unless you can get someone else to pay for them like from a taxpayer bailout or from donations from the ueber wealthy who are passionate about sports.