Honestly, if 13M is all it takes I will be surprised... For now, maybe that is the case. But not forever.
Honestly, if you look at how much you spend on entertainment / football (tv subcriptions, tickets, parking, etc. etc.) if every ISU fan that goes to a game (61k+) gives $10/month that is over $600k per month, $7.2M / yr. There are many fans (like me) that can't go to games (live in NC). So, plenty of opportunity for ISU to bring in signficant NIL dollars if everyone that enjoys ISU football were to give a relatively small amount of their monthly entertainment budget to fund this. That is counting on 0 major gifts. A few of those could easily double that amount.
My point is, ISU can compete at those levels (5M - 15M). It will likely take a different path - many giving small amounts vs. a few large gifts.