Let's step back and pretend like the TSA/police never engage in civil asset forfeiture in the first place. That issue aside, this is still a
colossally stupid way to make a transaction.
A thousand bad outcomes that are possibly more likely than this scenario could have happened. The bag could have been lost in the taxi, lost by the airline, stolen by a passerby, left at home, and the list goes on.
Has this guy ever heard of Western Union? Bitcoin? A cashier's check? Anything else besides a suitcase full of cash?
This method of making a large transaction is so stupid that it's hard for me to even blame the government for considering it automatically suspicious. Of course, having no due process surrounding civil asset forfeiture is not right, but that doesn't mean that this transaction isn't suspicious.
I'd go ahead and play devil's advocate here: the only reason to carry this much cash is to do one of the following:
1. Evade sales and income tax (You can say this isn't your problem, or that the government should take less of our money anyway, but countries that have high tax avoidance rates have poor infrastructure and public services – tax avoidance hurts honest people the most)
2. Make a transaction to exchange illegal goods or people
It's entirely possible that this guy's story is just a lie. I think it's naive to pretend that this guy isn't likely to be connected to organized crime. That's the whole "organized" part of it: they're going to be armed with a good story and disciplined behavior, not like the people you see on Cops admitting guilt the second a beat cop starts asking questions.