If I sell something and give the buyer a choice of a smaller immediate payment or larger total payments over a longer period of time, it is a ribbis issue, despite the fact that it’s his choice. there is a chov, and the extra money, based on the extra time, is schar hamtonas maos. My question is, has a chov been created here with a raffle.
There are ways around ribbis, aside from heter iska, such as involving karka in the transaction. It’s also not clear that there’s ribbis with an institution, although it’s certainly better not to rely on that.
I wouldn’t jump to conclusions that there is ribbis (they’ve probably dealt with it), but I think it’s an interesting shailah.