I think that's out of date. He links to a study showing interchange revenue net of rewards showing up to 3% by high FICO scores. (Just at a gut check that seems crazy to me, since interchange revenue doesn't really go much above 3%!). But that's from 2013. I remember when Fidelity launched its 2% flat cashback AmEx back in 2003. People didn't really know if it would be sustainable. Now 2% is a dime a dozen.

The most recent I've seen otherwise is this Federal Reserve study[0] from 2022. It finds that the marginal return on swipes is actually slightly negative because of how juicy rewards have gotten, and 80% of their profitability comes from interest (with most of the rest fees):

> we find that, on average, the credit function makes up approximately 80 percent of the credit card profitability, whereas the contribution of the transaction function is slightly negative, as rewards and other expenses on credit card transactions outpace banks' interchange revenues.5 In addition, fees—in particular late fees—comprise approximately 15 percent of credit card profitability.

[0] https://www.federalreserve.gov/econres/notes/feds-notes/cred...