Depends on how much frugality plays into it - you control your tax rate a lot more in retirement. If you spend 20k per year or less (Married filing jointly), and you structure your withdraws properly, you will be paying 0% in income taxes (federal any way). And you can pay little to no taxes when you are in the draw-down phase on significantly more spending than that as well - that's currently just the "obvious" amount you can get tax free with the standard deduction and two exemptions.
That right there is the beauty of the traditional IRA / 401K - when you're saving, you're saving your marginal tax rate which for most people is at least 10%, and can be as high as 39.6%. If you go the "no-other-income" route in retirement, you're paying your effective tax rate - and on presumably a lot less income than you were earning before retirement - all of that tax free space, and zero taxes on capital gains / dividends work to make your tax bill in retirement very low, if you do it right.