As this WSJ piece from December on the matter of the GAO estimating $108 billion in writedowns (probably a low figure, as they admit their accounting on the matter is crap) puts it:
"To help pay for ObamaCare, Democrats simultaneously federalized the student loan market and projected fictitious savings, all while adding more than $1.2 trillion to the federal balance sheet... then cited the government “savings” to peddle the fallacy that the feds make money off student loans—a pretext they then used to sweeten debt forgiveness plans that have helped keep default rates artificially low."
http://www.wsj.com/articles/obamas-giant-student-loan-con-14...
https://www2.ed.gov/about/overview/budget/budget14/justifica...
In FY 2016: 100-112% https://www2.ed.gov/about/overview/budget/budget16/justifica...