CLEMSON, S.C. — Clemson safety Van Smith drives a BMW, but the car is long past its days as a ride of luxury. It is a 1999 sedan with 300,000 miles on its odometer. Like many college students, Smith holds his breath every time he turns the key in the ignition — hoping the car starts. One day in November, it didn’t.

“The starter went out in the middle of campus,” Smith said. “It cost $400. I had to get it towed up the street. Not cheap.

“So, yeah, the $388 stipend we get? I need that.”

Smith was referring to the $388 monthly stipend that Clemson players receive during the academic year. The payments, approved by the so-called Power 5 conferences in 2015, were created to supplement players’ athletic scholarships to meet what is known as the full cost of attendance. They vary, sometimes widely, from college to college, but they are paid to almost every player in major college football, including the ones from Clemson University and the University of Alabama who will play for the national championship on Monday.

The stipends, which are meant to cover costs not included in a traditional athletic scholarship, have been allowed since before last season. The move came after the so-called Power 5 conferences, acting with the autonomy newly granted them by the N.C.A.A., voted to enlarge the grant-in-aid given to scholarship athletes to include the full cost of attendance. That figure is the more expansive measurement that every college already calculates, and it encompasses expenses like rent, cellphone bills and trips home.