[RadioAstronomer]

Why I did not carry cash to buy my Vette since I crossed state lines to get the one I wanted.

Cash is pretty much dead anyway. I almost exclusively use credit cards for everything I do including paying all my bills online.

I almost never have more than 10$ on my person.

[conservative in nyc]

It's not illegal (but is awfully foolish) to walk around the United States with more than $10,000 in cash. You need not report it to anyone.

I think that if you paid for your Vette with cash, the car dealership would have had to report the transaction to the Department of the Treasury. In fact, if you paid with a check, the bank probably had the same reporting requirement. But you need not report anything if you are just walking around spending wads of cash inside the U.S. Just don't try to leave the country with over $10,000 in cash without reporting it. They'll take your money away and could even throw you in jail.