The author mixes in interest, interchange, and fees. What he calls &quot;fees&quot; are actually interchange, and it&#x27;s a relatively small line item in bank&#x27;s P&amp;L.<p>The main source of business income is interest. And interest is so high because it has to offset losses from card members that stopped paying. Remember that credit cards are unsecured products. Banks typically recover only about 20% of the default amount, the rest is gone.