The data on subsidies is pretty revealing. The whole MAC and the rest of the G5 live off of student fees. As to sustainability, I guess it's a matter of when enough students/parents rebel. I am not making a pro or con argument because it's been discussed ad nauseam here, but it is a simple fact that most revenue for most (maybe all) G5 athletic departments comes from mandatory student fees.
http://sports.usatoday.com/ncaa/finances /
As it relates to student fees, and parents/students rebelling, what is the approximate number each student fee might be? My math based on the link above, and then looking up the enrollment figures from Fall 2014 (same timeline) is about $479. I suppose that is a higher number than I expected. On the other hand, it's a fraction of the costs that are paid if it's accurate.
(Enrollment stat site:
https://www.ohio.edu/instres/enrollstats /)
The "general fee" for a full-time student is $671 per semester.
https://www.ohio.edu/finance/bursar/ohioguarantee16-17.cfm That said, the fee covers more than painting the red ledgers of athletics black. It covers things like access to the rec center, arts programs, student groups, etc. This makes it harder to pin down the exact cost per student for athletics, but according to an A-News piece discussed here last year (*ducks as certain posters throw things and accuse the A-News of being biased/evil/athletics-hating), it is $850 a year.
http://www.athensnews.com/news/campus/ou-s-m-athletics-bu... Whatever it is, that amount is not optional, and some students are starting to make noise about it.
http://www.athensnews.com/news/campus/survey-ohio-u-grad-...