This keeps coming up, most recently in a thread over here. I finally did some research. FWIW:

Note: UM System and MU are, of course, different entities but I could only find UM System revenue and expenses. I could only find MU revenues. So FWIW:

Total revenues for the UM System last year were about $2.62 billion, with expenditures and transfers of $2.64 billion

PDF link: https://uminfopoint.umsystem.edu/media/fa/budget/operating/FY2012BudgetBook.pdf

I can’t find an expense detail, but Mizzou was responsible for about $2 billion of that total:

Link links to a PowerPoint: http://mubudget.missouri.edu/presentations.php

The athletic department had revenues of about $64.14 million and spent $64.16 million:

PDF link:
http://media.kansascity.com/smedia/2012/07/07/20/24/11asHp.So.81.pdf

So if you say that the MU athletic department spends $64 million out of revenues for the overall U of $2 billion, that’s 3.2 percent of the Mizzou’s overall revenue, or 2.4 percent of the UM System’s revenue. And it doesn’t take into account the amount of the AD revenue that’s self supporting, which from a cursory reading of the Star link is nearly all of it.