The needs of retirement should scale with inflation, so that means you also need $3 million today (in today's dollars) – which is rather high. $600,000 is not too far off what is the minimum recommended amount of saving to retire for 20 years on today, so it seems they simply adjusted that figure for inflation and then forgot that the income used to build up those savings also goes up with inflation.
$30K per month, even 40 years from now based on 2% inflation, is equivalent to $13k per month today. You'd have to try really hard to not get by on that.
I assume you mean $30k per year. The recommended is more like $700,000, and that factors in your pension, but we're just using approximate figures here. Still, $30k per day today is quite doable for a retiree. What are you going to spend your money on, exactly? You've already purchased everything you need by that point in life, so you're just in maintenance mode.
That's true. As a non-American I forget that you have to worry about such things. The $3 million is in line with what I would expect will be needed in 40 years, sans healthcare costs. It is, adjusted for inflation, in line with what is recommended today where healthcare is provided to all. So, it seems it seems that figure assumes that US healthcare will be 'free' in 40 years?