Heh I may have exaggerated a bit to make a point ;) realistically its more like every 2 years or so, and partially because I started from a junior role in an enterprise environment and worked my way up to independent consulting.

start with very low income and only have a small number of years in industry.

15k -> 30k -> 60k -> 120k

For the first couple of years it's possible. I'm not sure it's going to work past year 3 or maybe 4.

Part time junior -> full time junior -> senior -> lead over 5 or 6 years.

Also if you have stock at a successful company in the past couple of years things have gone vertical.