I agree that one single metric like APR is not sufficient to compare all possible cases of lending without making some options to look worse than they really ar

I agree that one single metric like APR is not sufficient to compare all possible cases of lending without making some options to look worse than they really are. But if you were a safe enough borrower to even get a $100k loan, then you're sfe to loan $100 to for a tiny return also. Payday loans probably tend to be for people who can't get better loans of any size.