It isn't always about the money

If he finishes the current year "successfully," I doubt, after 2 full years of starting, there is little he stands to gain by staying in college. In fact, he has more to lose in re: injury. If he is a pick projected within the top 15 this year, I doubt he improves that by staying in college.
Current projections have him within the top 5 qbs. Chances are he isn't going to be taken before Moore or Manning (even though many scouts are not sold on him yet). After that it seems it is Carr, Mensah and Sayin in that order, although I believe Sayin won't be rising given OSU stellar talent tends to make him look better than he is and OSU isn't exactly QB U at this junction. The 2028 qb draft class looks weaker than the 2027 one but there are always going to be guys who emerge out of nowhere.