We paid pretty close to the University estimate for room and board, but my daughter chose to live alone or with just one roommate after she left the dorms. She lived two years in a 1 BR in a newer, furnished complex within walking distance of campus and one year in a 3 BR house about 6 miles from campus. Her rent and utility costs were more than twice your $400/mo. estimate. Her food costs went down after freshman year, and while Dining Dollars are still mandatory after freshman year, if you don’t use them you can request a refund at the end of the year. My daughter rarely used any Dining Dollars, so she always got a pretty big refund. My daughter also kept her book expenses pretty low. She rented or bought used books, she would ask profs if prior editions (WAY cheaper) were acceptable and they often were, and she found a surprising number of books free online. Finally, her transportation costs weren’t that high for living 12 hours away. She only flew home twice in 5 years; she has a car and drove herself down and back from school at the beginning and end of the year (and junior and senior year she spent summers in Tuscaloosa, so no need to even do that).
ETA: as for security deposits, my daughter had no charges for her two years in the apartment complex and there were no mandatory cleaning fees. The house she’s in this year has a mandatory cleaning fee in a stated amount (and she will move out without cleaning because of that), but except for that I expect that she will get her security deposit back.