Not sure where the scam is. At a glance it doesn't seem to be exploiting some kind of rounding bias past a threshold. It just happens to keep a strange remainin

Not sure where the scam is. At a glance it doesn't seem to be exploiting some kind of rounding bias past a threshold. It just happens to keep a strange remaining balance that you keep anyway. Nobody throws away the cards anymore because now it costs a fee to get a new one. So you end up always spending the money you put in.