According to the story I heard about that fella's case, the officer that stopped him said his having $2000 cash WAS probable cause because he was close to the Florida state line (in Alabama)... them finding 2 joints in his luggage didn't help. Went from bad to worse when they didn't pick up his clothing and luggage (minus 2 joints) until AFTER they were good and rained on.
I am easily intimidated, especially by those in uniform and I've been told by LEO friends that saying no IS probable cause in the minds of LEO, so just do it cause when one says no, they are going to jail, one way or another.
The first time I had my carry on checked was when they had a set up at the gate. The TSA guy asks “May I check your bag.” I said “No.” His face got tight and I saw this was going bad in a hurry. I asked him if I had a choice. He said no, I would be detained. I suggested that he not ask “may I.
In some jurisdictions they even have a form to sign when they do consent searches so the guy doesn't challenge the search in court.
If they find me with a bunch of cash I would tell them what I was using it for. You have better luck of keeping your money from a seizure happy cop if there is a plausible explanation. Once they get it you are going to spend a bunch of time and money getting back.