The good thing about a law targeting billionaires (and taxing their wealth at 10%) is that the administration costs can be at least $100m per investigation and still break even.
(Admittedly at the bottom end someone might manage to sneak in under the threshold, making the investigation a waste, but there's no harm in the bureaucrats starting with the richest person and working their way down the list, gaining skills and efficiency as they go).
Even if all the money that the government collects ends up going to pay the investigators, at least that would be creating thousands of decent jobs. Also, assuming a balanced game, if the investigators are being paid $100m to find evidence then the billionaire would have to pay a similar amount to hide evidence, which means they might as well not bother hiding it.
I'm imagining that the wealth tax would only apply to people with more than $1bn in net assets, so the overhead for almost every tax payer is to simply tick a box each year saying "I am not a billionaire".
More precisely, the law would require anyone with gross assets above some threshold, say $500m, to report the value of those assets to the IRS every year, based on some simple valuation rules, like "How much did you pay for the asset?" and "What is the market value of those shares / cryptocurrencies?". Only assets worth more than $1m would need to be declared.
Then, as I say, the IRS can go down the list of people with the most assets and do a more thorough audit, to make sure their valuations are correct, while also making sure that there aren't any billionaires who have forgotten to file, since it should be hard to hide that much wealth.
(Admittedly at the bottom end someone might manage to sneak in under the threshold, making the investigation a waste, but there's no harm in the bureaucrats starting with the richest person and working their way down the list, gaining skills and efficiency as they go).
Even if all the money that the government collects ends up going to pay the investigators, at least that would be creating thousands of decent jobs. Also, assuming a balanced game, if the investigators are being paid $100m to find evidence then the billionaire would have to pay a similar amount to hide evidence, which means they might as well not bother hiding it.