[sksk]

One more thing. 30 days is not the right point as payments are usually due 28 days after the statement is issued and most people (people who carry a balance) pay closer to the end -- all this while things are getting compounded. So your 0.53/mth will be more like 0.9/mth in practice.

As you could this gets into a lot of nuances on how people use credit cards today. We attempted to keep things simple and it lead to a totally different issue, which you raised. We will try to revise it to make it more like a what a user will do over the life of their debt and compare. Again, financial delta for each user is not the issue but rather the 'fairness' of this whole thing -- how does compounding really benefit the consumer?