Is There a Sin of Usury in Money Lending?

The article is on things that are like interest, but aren't. You know, there are other kinds of consideration that you can take from money lend. And so he's talking about basically cases where you change the price in this specific objection or in this reply. But to say that you can offer your goods for sale with a discount for advance payment amounts to inducing usury and conflicts with what he says in Article 4.