Totally agree with this. Dug up some attendance data, which is not as good as TV numbers but a lot easier for somebody like me to understand.
2016-19 Average Attendance
BYU - 56,715
UCF - 40,113*
Boise State - 32,634
Cincinnati - 32,131
*This jumps up to about 44,000 for just 2018-19
2019 Big 12 Average Attendance:
Iowa State - 59,794
West Virginia - 55,907
Oklahoma State - 54,817
Texas Tech - 53,418
Kansas State - 48,818
Baylor - 45,517
TCU - 42,881
Kansas - 33,875
2019 Notable Power 5 Average Attendance:
Utah - 46,462
UCLA - 43,849
Cal - 42,433
Arizona - 39,532
Stanford - 37,018
Oregon State - 32,424
Washington State - 28,541
Georgia Tech - 44,599
Pitt - 43,372
Syracuse - 42,164
Boston College - 34,185
Wake Forest - 26,999
Duke - 25,811
Minnesota - 46,190
Indiana - 41,244
Maryland - 37,812
Illinois - 36,587
Rutgers - 30,082
Ole Miss - 48,233
Vanderbilt - 26,288
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From this alone, BYU is easily in the P5 ranks and would rank 2nd out of 9 in the Big 12. UCF is also very solidly in range. And based on TCU's data, Boise State or Cincinnati would receive a power-conference bump that would still keep them on the low end, but certainly not the lowest among the Power 5.
There are definitely schools in Power 5 leagues that are only there because they always have been. They drag down the conference's financial value and take far more than they offer. The schools the Big 12 is considering would not do that to the existing eight.
What I really wonder is the what the increase in attendance will be for the schools outside of BYU once they would join the B12. What does that do for a Cincy, UCF, UH and then some of the less likely additions like ,Memphis, USF, CSU, BSU