Is the merchant Credit card discount rate revenue or expense?

The Credit Card Discount Rate is revenue for the CC Processing company, and an expense for the merchant who submits the credit card. It's nothing to the CC holder. So you use your cc to buy socks online from socksonline.biz. Socksonline.biz uses 10th National Bank to process the transaction. The Discount Rate is paid by socksonline.biz to the 10th National Bank. Therfore, it is revenue for the 10th National Bank and an expense for socksonline.biz.