The consumption will not be flat at $100,000, to be sure, but the more one makes, the smaller their portion of total income is consumed in a year. A regressive tax is inevitable in the higher income brackets.
That's assuming an undividual at $1m per year has the same lifestyle as the person who makes $100k. You and I know that's simply not true. While many do save a lot of it, most simply buy more expensive homes, cars, clothes, food, boats, trips, etc.
I guarantee you John and Theresa don't save. Why do they have any reason to save? They have enough money to make $30 million a year in tax-free bonds. They splurge.