TSA detains man for simply having cash on him?

[JALU3]

How much cash? if you are transporting over X amount, it's illegal.
I think it's like 10K

Edit:
Here are the items you are required to declare. But of course listening to this video, those items that I will list below do not apply.

Items you purchased and are carrying with you upon return to the United States.
Items you received as gifts, such as wedding or birthday presents.
Items you inherited.
Items you bought in duty-free shops, on the ship, or on the plane.
Repairs or alterations to any items you took abroad and then brought back, even if the repairs/alterations were performed free of charge.
Items you brought home for someone else.
Items you intend to sell or use in your business

Here is a sample form.