It's a big number, but it's often tied up in housing in VHCOL/HCOL areas. It also doesn't mean much re: not needing to work in these areas.

Also given retirement in US is self-funded via saving/investment instead of pension, someone who wants a comfortable retirement in many areas of this country needs $1M NW by 65 to generate a $40k/year income (above the social security payments which don't go so far) at safe withdrawal rates.