Per InForum.com:
... South Dakota State spends $8.8 million a year on football. North Dakota State is next at $6.41 million and the rest of the league goes as follows in millions: North Dakota $6.02, Missouri State $5.24, Southern Illinois $5.21, Illinois State $4.8, Youngstown State $4.71, South Dakota $4.45, Murray State $4.03 and Northern Iowa $3.8.
Note: SDSU's number includes debt service on stadium improvements.