[andthenzen]

Worth noting that this varies heavily by issuer - I checked out the most recent 10Ks for Amex and Discover (Visa and MC are networks and as such, operate off interchange, not interest, and I tried looking at Chase's 10K but it was too complicated for me to figure out the revenue breakdowns for their consumer card business)

* Amex had 67b in interest + non-interest revenue, of which the single biggest driver was discount revenue (aka interchange) at 33b. Interest contributed 20b, card membership fees contributed 7b, and services fees and other were ~7b combined. Amex's target base is wealthier individuals.

* Discover had 14.4b in credit card interest revenue and 1.4b in net discount and interchange revenue (meaning after paying rewards). Discover caters mostly to what the financial industry would euphemistically call "subprime" creditors.