bundle of banknotes; stack of bills
Refers to a physical wad or bundle of paper money, often bound together. Commonly used in news and everyday contexts.
The culprit fled with a bundle of banknotes.
A stack of bills was left on the desk.
large sum of money
Used figuratively to emphasize a large amount of cash, not necessarily a physical bundle. Often appears in expressions like 札束が飛び交う or 札束で頬を叩く.
That politician tried to solve the problem with a large sum of money.
He paid for the car with a bundle of cash.
The bank clerk carefully counted the bundle of bills.
The big corporation pushed the negotiation forward as if slapping people with a wad of cash.
It's said that huge amounts of cash change hands in that industry.