Bank of America built their own cloud. They say they save 2 billion a year.
https://www.businessinsider.com/bank-of-americas-350-million...
It seems no company wants to be in the business of in house IT Systems. They think moving all their infra into the Cloud absolves them of all the responsibility of owning it themselves, they don't give a shit how much it costs but then tell you everyone has got to save money and tighten their belts.