Bringing St Francis and Dartmouth to South Bend doesn't cost much more than the price if a bus ride, a night at the Super 8, and a bag of balls. Chicago State doesn't need the Super 8 stay.
Most of the non-conference teams ND plays at home are inexpensive. The tougher games are at neutral sites where both teams are paid well to appear.
Some of examples:
Duke's non-conference home games in 2016-17 were Marist (276), Grand Canyon (131), William & Mary (110), Appalachian State (300), Maine (323), and Tennessee State (161) plus Michigan State in the ACC - Big Ten Challenge... 2 games vs 300+ RPI.
UCLA's non-conference home games in 2016-17 were Pacific (223), Cal Northridge (313), San Diego (98), Long Beach State (213), UC Riverside (330), Michigan (sucks), UC Santa Barbara (324), and Western Michigan (174).... 3 games vs 300+ RPI.
Villanova's non-conference home games in 2016-17 were Lafayette (321), College of Charleston (62), Saint Joseph's (201), LaSalle (137), Temple (135), and American (310)... 2 games vs 300+ RPI.
Marquette's non-conference home games in 2016-17 were Howard (338), IUPUI (218), Houston Baptist (176), Western Carolina (271), Fresno State (76), Wisconsin (ongoing home-and-home), St Prancis PA (257), SIU Edwardsville (333)... 2 games vs 300+ RPI.
We might not like it, but ND's scheduling is standard practice in college basketball.