In the olden days if we spotted a customer ringing up a colossal bill, we would tell them. These huge Amazon bills are fast but still multiple days. They can trivially use rolling-projection windows to know when an account is having a massive spike.

They could use this foresight to call the customer, ensure they're informed, give them the choice about how to continue. This isn't atomic rocket surgery.

"Oh but profit" isn't an argument. They are thousands of dollars up before a problem occurs. The only money they lose is money gained through customer accident. Much of it forgiven to customers who cannot afford it. It's not happily spent. They can do better business.