Just like a small business is less regulated than a large one (often), or how smaller incomes are taxed simply while those with more money/more complex assets get audited more - the ultra-wealthy will certainly have more of their assets audited, and yes, they will have side channels to evade taxes. That doesn't mean we don't try to tax them.

When someone out in the open owns 75 cars, a private jet, and a $250,000,000 townhouse in Manhattan and another $5 billion in stock, it's pretty damned simple and not wholly intrusive to look at that and say "alright..."

I'm not defending the entire concept of a wealth tax, but I am saying it isn't as dire for _everybody_ that you say it is.