Orange County CA, where I live, where the average house in our ward now costs well over $1mm. Now obviously salaries pay more here to compensate for that. But trying to retire on $100k at age 40 in Orange County with a mortgage and four kids would be very difficult to do.
Obviously it is much more doable in other locations. I have lived in California and just outside NYC for the last 10+ years and cost of living is really expensive in both areas so that is the lens I was looking at this through. Living in Pocatello, ID or Parowan, UT would be completely different.