NU being a private school doesn't have to release as much info to the public as state schools do. Probably all NU revenue goes in principle to the central admin. They then decide how much to allocated to the AD's budget. They could allocate as much or as little as they wish. But they probably won't allocate MORE than the revenue NU gets from athletics (all sources considered).It has been reported that the BTN money does not go directly into the AD. Is that still a fact ? Seems that with BTN cash increasing, it might go a long way to balancing the AD budget, as well making more cash available for coaches salaries.
There are always accounting issues. For example, NU could allocate the AD a lot of money, but some of that money could immediately come back to the central admin as payment for the tuition of the student athletes. At the end of the day it's all NU's money.