SIn your scenario, this couple saved up 2.5 million by 50 but were eligible for traditional, deductible IRAs their whole careers and are now eligible for less than average social security? All while spending $100k above and beyond payroll taxes?
This couple managed to save up $2.5M by 50 while spending $100k per year, after tax? So they probably made $250k, putting them in the 33% tax bracket while working (current rates). So since OP's calc puts them in the 12% bracket now that's quite an improvement IMO. So yes indeed; taxes are lower in retirement. Obviously you still have to account for taxes, which vary depending on your spending level. You only need $25k/year you can probably assume zero tax. You need $100k? No you will have to pay some tax. I'm pretty sure everyone here are well aware of this so not sure what the revelation was?
The revelation is that said couple will likely have $0 in taxes for a number of years, even at $100k in spending, however that will increase to $5-10k later in retirement. So if said couple were strictly planning on following the 4% rule, they might get surprised in their 60s when their inflation adjusted spending level also gets hit by tax increases.
Really, I had two revelations. First, that we might be able to pay $0.00 in Federal Income tax for a number of years, and second, that will eventually stop when we have to pay income tax on tax deferred accounts and social security. (Now once we start getting social security it will likely offset the taxes on the IRA/401k money.) Basically, previously I was modeling too much spending on taxes, and then modeling not enough in taxes.
For the couple it may look like this (again 2018 dollars and the years are not necessarily exactly when these things would occur, depends on when they hit their tax deferred accounts and start getting social security):
2017 - 6 figures during accumulation
2018 - 6 figures during accumulation
2019 - $0.00 in taxes ($100k comes from cash on hand, harvesting capital losses to offset capital gains, $25k in dividends and interest, $26k deduction, $0 in taxes)
2020 - $0.00 in taxes ($12.5k interest/non-qual div, $12.5k qual div from taxable acct, $50k of stocks sold mostly already taxed, $25k capital gains. after $26k deduction = $0)
2021 - $0.00 in taxes ($12.5k interest/non-qual div, $12.5k qual div from taxable acct, $50k of stocks sold mostly already taxed, $25k capital gains. after $26k deduction = $0)
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.
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2030 -
$7,500-8,000 in taxes ($75k IRA/401K, $25k social security. $100k taxable ordinary income-$26k std deduction leaves $74k at 10-12%.)
So it seems that the trick will be to maximize converting to roth in our fifties, but need to avoid ACA cutoffs, and capital gains cutoffs.