How can you have a wealth cap?
State you can't have more than X dollars in the bank. Okay, can I use my money to buy things (e.g. property)? Should you value my property at the market value as "dollars in the bank"? What if I buy my property and it appreciates, would it get confiscated? Would police come to my home and forcibly move me to a home below the cap?
Can I own or invest in a business? Do we mark that at "market value"? Who sets this market value? What happens if my business does well, too well in fact and now my market value is more than the allotted amount.
It's impractical and its not entirely clear what "million dollars in the bank" really is. The fact is that very few wealthy people just have money sitting around in a bank. And when you try confiscating other types of wealth you realize how impractical it is. Income cap becomes equally complicated when you count income as money a business you own made and reinvested in itself