Sorry for the delay in response, I was busy for a while.
Maybe not so simple, Werewolf
You pay 20% to the feds. Are you married? Any children?
By my best figure, you'd end up paying ~19% if you're single. Less if you don't spend your entire income. Do you invest any?
You see, the sales tax rate is 23% inclusive, which is a comparable rate for how an income tax works. You see, with income tax the money you're using to pay the tax is also taxed.
I drafted up an excel spreadsheet that figures it out, including a quick calculater to switch between after price tax and inclusive tax rates.
Results:
Money Earned: $50,000
Money Spent: $50,000
Poverty Level $9,000
Sales Tax Percentage: 30%
Tax rate: 23% *Note: You have to figure the tax as an Inclusive tax to make it like income.
Taxes: $9,461.54
Income tax % equivalent: 19%
Making half the income?
Money Earned: $25,000
Money Spent: $25,000
Poverty Level $9,000
Sales Tax Percentage: 30%
Tax rate: 23%
Taxes: $3,692.31
Income tax % equivalent: 15%
Double?
Money Earned: $100,000
Money Spent: $100,000
Poverty Level $9,000
Sales Tax Percentage: 30%
Tax rate: 23%
Taxes: $21,000
Income tax % equivalent: 21%