The Manning School of Business at the University of Massachusetts-Lowell was last year's lowest-cost online MBA, and the school kept its pricing structure unchanged. So why doesn't Manning again boast the lowest cost of any online MBA in Poets&Quants' yearly ranking? Because North Dakota lowered their price by 15%, and because of the addition of Rogers State to the ranking. The most expensive: No. 2-ranked Carnegie Mellon Tepper once again, which will set students back more than $141K.