The calculation seems off by almost one order of magnitude. Even investing 10$ a month for 50 years (!), and managing to get a net return of 7% for such half a century, will build up only about 50K. Except that, by that time, even a modest inflation rate of 2.5% will make it worth less than 15K in real terms.

Which makes sense, otherwise any childless person in the West with a decent job could save 1k a month and retire with 10M, or a Google SWE5 living with a SWE4 lifestyle could save 10k a month and retire with 100M.