The industry has been investing heavily in digital methods of exchanging money, including a U.S. payments network called Zelle. But the cost of processing paper checks and carting around dollars and cents still weighs heavily on big banks, and it may take 10 to 15 years before that problem goes away, Moynihan said at a conference organized by The Clearinghouse, a trade group focused on payments.

“Even though mobile wallets, credit cards and debit cards all grow, you still have a lot of cash and a lot of other things, so it will take time for customers to change,” he said in an interview with Reuters following a panel discussion.

Roughly 10% of Bank of America‘s costs come from moving coins, currency and checks throughout the banking system, Moynihan said during the panel discussion.

The Charlotte, North Carolina-based bank reported $32.9 billion in operating costs for the first nine months of this year.

Credit cards worked as a profitable payment system for the banking industry for a long time. However, a 2010 financial reform law placed limits on fees banks can charge to process transactions, making the business less lucrative.

“We had this great system called Visa and Mastercard, which we built for years,” said Moynihan, “but it gets attacked on expense.”