IMO the estimates on the iSU website are high. My daughter is a sophomore, and last year we came in around $17,500. She lived in MWL and had a meal plan. Her books were less than $300 for the year. She works in Athletics, so that was her spending money, plus working over Christmas break, and the money she saved from working in the summer before going to school.
Things to remember - some of the textbooks are electronic and you will be charged a fee on the ubill. Any scholarship money is split over each semester not all at once. So if you kid gets a $2500 scholarship, they get 1/2 in the fall and the other 1/2 in the spring. Same thing if you have/use a student loan, you get 1/2 in the fall and the other 1/2 in the spring. Also, you do not have to take the maximum amount offered.
If bringing a car add $119/year minimum for parking on campus. Attending athletic events and getting a sports pass, add $300. If you decide to do a payment plan for tuition, there is a fee.
My daughter took her student loans both semesters in addition to the money we had set aside for school. We then paid on the student loan immediately, so her loan for the fall semester was paid off in December and spring semester was paid off in May. The loans are in her name, so it is helping her build her credit, and we were able to repay them interest free because of student loan payments being suspended due to COVID-19. We are following the same playbook again this year in regards to loans. The only thing that changed is she moved off campus and no longer has a meal plan. Our gift to her when she graduates will be that she is debt free and can start her professional career without the worry of student loan debt.