I know it’s just recently rates have bounced to these levels, but $1M will throw off about $50k/year in interest income. That’s an above average salary in a majority of the country. And it’s worth more than a salary; you still pay income tax, but there is no social security withholdings.
Plus family size. And I suspect that there’s a lot of influence from what the respondents’ dream retirement would be like, rather than merely what they need to maintain their lifestyle without a weekly paycheck.