There are some saving in moving to FCS, including 22 less scholarships, lower coaching salaries, and perhaps half the total staff. On the other hand, you lose the playoff money, and the MAC TV money. Paid attendance at games is significantly less, with an average of 8,200 nationwide. Furthermore, you lose whatever "value" is obtained from the nationwide exposure on ESPN, etc, and the community loses perhaps half of the economic impact of having home games, since attendance is about half. So, making a rough guess, you save about $2m in expenses, and give up about $2.5m in revenue, plus the exposure. Note: for UConn, which used to be P5, the expense and revenue drops would both be much greater than $2m, but I don't have any guess as to how far either would drop.

I don't think it's a coincidence that leading FCS teams pretty much all want to be G5, while G5 teams virtually never drop to FCS. Idaho did, but only because they had no conference willing to take them, and weren't viable as an independent.

Now, if you ask, it is financially better in Division II or Division III? I think the answer to that is certainly a "yes". I see either as a viable choice that could be made someday.