Also, even if it had to pay a little bit when adjusted for the cost of borrowing it's still a massive win. After all the government is nominally not a for-profit institution but rather an entity that helps their citizens (or at least tries to). But in this case it definitely turned out a lot better than one might have predicted at the time the program was launched.
In real terms, the Treasury should have recovered $467B 2014 dollars for its investment to have a 0% real rate of return. In fact, $25B real 2008 dollars were given to banks and never recovered.
Let me illustrate this with an example:
1. I borrow $1M at 5% p.a., for a year
2. I lend out this $1M to someone else at 7% p.a., for a year
3. A year passes
4. My debtor has not defaulted! Great, I collect my $1.07M
5. I pay back $1.05M
6. I am $20k ahead
TARP was a Treasury program, so wouldn't it have been financed by Treasury notes, which averaged about 2% during that period?