EDIT: Regarding the argument in this subthread regarding interest rates, the common mistaken assumption seems to be around what constitutes the "principal" here.
In "steady state", there will be very little money flowing out of Even's coffers into the user's wallet. So the "average" amount loaned to the user is likely to be close to zero... or even negative (in case the user makes a bigger paycheck than usual). So the interest calculations only make sense on that amount. Not the entire amount of money that the user made. The actual "interest" payment in those cases could easily be in 100% + range or more for the average user.