...he might be arrested if he behaved the way cops - and especially US cops by the way they're portrayed in books and films - don't like to be behaved to.
This is ultimately the real point - cops everywhere, and particularly american cops, are just thugs. The system, though a violent, brutal, and dangerous one to the lower classes, ultimately will not actually prosecute the worker for having $4,700 cash, since there is no practical reason to do so. However the cops will beat him silly for being uppity.