It's actually the opposite of payday loans. For example, if someone were to take a 1 month loan for $200, at 15% monthly interest, then they would pay $230 at the end of the month.
In the UK at least, loans must quote an Annualised Percentage Rate (APR), which is the IRR (Internal Rate of Return) over a year. So, any adverts or contracts for this 1 month loan would have to show prominently '435% APR'.
The loan is framed as '435% APR', when in fact you're paying $30 for a $200 1-month loan.