And so it's no surprise when normal methods of investigation become almost useless. It's no bad thing, either, or almost everyone would be in jail for something. The problem is too much law, not too little surveillance. The answer is not to treat ordinary people like money launderers but to focus the resources of the legal system on behavior that hurts others in a direct way. In a free society, there's no need to turn private businesses into spy agencies.
Most laws are self-reporting.
There's no need to force bankers, grocers or neighbors to report that kind of behavior, or to threaten them with the forfeiture of their property if they don't. The complexity of our lives and the government's lack of knowledge about them are a bulwark against authoritarianism that is as important as the Constitution. Have Failed, all through history governments have struggled to collect more information about citizens. But the more they strive, the more unlikely it is that their goals can be compatible with the complex, fast-moving life in free society. No American citizen should be treated like a suspect.