You have to declare more than $10,000 IIRC when traveling over the border. When taken into account with all the other suspicious activity, it's worth a mention.
The point is that the totality of their actions are not supporting their story very well.
Not that I agree with it, but cash definitely can be considered criminal in large amounts. Having a few hundred to a few thousand is enough to be arrested in the US, assuming you're not protected by celebrity.
We don't (and shouldn't), but I don't know of very many people who go on vacation with $16k of it. Like what the hell were they gonna spend that on? A pallet of novelty keychains?
Basically, yes?
actually over $10k without declaring it. But the point is that they were not tourists that got lost. Tourists carry credit cards and all. Why would they be carrying $16,000 (USD, unless it was the equivalent of it) if they're staying in CA?