I'm very glad we got to see Jazz and Allocer's training, though. It's certainly interesting. The art of deception... they are demons, after all, they're a little loose on the whole morals thing.
Ok I expected them to get duped, but I thought they're going to get scammed because of their own naivety not because their mentor literally sold them lol.
I mean Furfur's kind of a dick but I imagine he is actually doing this with teaching them something as a goal, and the clearing of his own debts as a side-benefit. I can only expect that Sullivan values his students quite highly, so this going wrong could have brought an unholy shitstorm down upon his (Furfur's) head.