Person 3 does not (and can not) spend his 8000 dollars all at once. He spends some and invests the remainder until he needs it, thus funding business activity that employs Persons 4, 5, and 6, who are also paid 10 and 100 dollars per year, instead of being unemployed.
Double Person 3's tax rate to 40%, reduce his disposable income to $6,000, and Person 6 and possibly Person 5 is no longer employed.
Your zeal to penalize Person 3 for his success costs Person 6 and Person 5 their jobs. Awesome compassion you have there.