I think the maximum merit at St. Olaf is half of billed costs (tuition, fees, room & board), which is $61K this year. So it wouldn’t come in under $30K but could be close. And it’s a great school.
There are lower-ranked private colleges in MN and IA that would probably come in cheaper. Many are Catholic or Lutheran. Luther, Gustavus, St. Benedict, St. Catherine, Loras, Concordia in Moorhead, etc.