[trominos]

This is a bad idea. Even if we accept that no individual can reasonably spend more than $200 million non-charitably (which is false), super-rich people tend to care deeply about money for its own sake -- I say this from limited but real personal experience -- and the accumulation of money tends to be a major factor in their motivation to continue to produce and to invest. If you impose a $200 million wealth cap, you are going to substantially reduce the wealth production of some of the most productive members of society and dramatically curb certain kinds of investment.

What do you get in return? Essentially the government receives a bunch of claim checks for wealth (remember that "money" itself has almost no intrinsic value; what we're after, from a macroeconomic viewpoint, is a maximal sustainable production of wealth). Your proposal amounts to reducing overall wealth production in exchange for increasing the government's buying power by a comparatively small amount. Forget ethical arguments against it; except in very extreme economic circumstances, it's absurd from a practical standpoint.

[_delirium]

This is assuming that the "super-rich people [who] tend to care deeply about money for its own sake" are actually "productive members of society" engaged in "wealth production", as opposed to merely being very good at rent-seeking (which gets easier as you get larger amounts of capital).