It doesn't cost the university anything more to add 85 students to classes. The marginal cost of adding those students to any given class is 0 since that professor is already teaching.

The actual costs would be for the other benefits. As I mentioned, there are economic costs if that spot in the freshman class could have gone to a student whose parents were able to pay full freight, but the main actual costs to the school are room and board plus other benefits since the school doesn't have to pay itself tuition.

Of course it costs ND the cost of tuition for scholarship players. As was pointed out, the spot would be filled by a paying customer otherwise. To ignore that would be ridiculous.

because they have football players on scholarship?