I think it’s totally possible to be making $75K/year at age 25 if you’re a software/electrical/mechanical engineer after completing your BS at 21 and MS as 22/23, and with 2-years of working experience.
However, is it really that easy to put away $2000/month ($4000/2 = $2000/person) while you still need to rent, put money in 401K, live, and then potentially get a mortgage and pay mortgage every month?
Saving 1.5M in the banks by age 40 is def. not that easy…if you’re getting married in your late 20s, buying houses, and paying for kids.
So I’d say your household income estimates is not based on average normal people.