That makes no sense. What if someone deposits a $20k paycheck into their bank and pays off credit card bills? How come banks don't shut those people down?
Or what if someone has a legitimate $5k bill to pay from a prepaid card?
They must be doing the shutdowns proactively. Not because they cost money, but because they MIGHT end up being illegal activity, and since they don't fit the pattern of 99% of their customers they're easy to spot.