You have made some strange assumptions here. I know you had to throw out numbers just to have some, but he turned 20 halfway through his second year. He turned professional in 2004 after the Olympics and ran his first pro race on 12/31/2004 the day after he turned 22. So the first year he was being paid was 2005 as a 22-yr-old.
I have no way of knowing what he gets paid, and I am not going to pretend, but $300,000 from "endorsements"? If you mean Nike salary, yes I suppose he could be making that much, but not every year. And the $200,000 figure? He doesn't race enough to pull that every year. I am sure he makes quite a lot from a NYCM or London Marathon appearance, but beyond that, how often has he raced in a paying race?
Bill Rodgers or Herb Lindsay or Greg Meyer raced at a paying road race more times in one year than Ritz has in the last 8 years.
But now, the biggest flaw: If someone earned $500,000 a year for 15 years that would make $7,500,000 gross. Even after taxes and living expenses you would have half that left over. Let's face it, a distance runner with a child isn't spending winters in St. Moritz and summers in Monaco. he would live the ascetic lifestyle needed and live like someone making $150,000 at most.
So after your career is over you would have about $3 or 4M. Just like I had $350,000 saved at age 35, when I graduated at age 27 and never made more than $45K at that age. And right now my one interest earning IMMA earns 1.73%. I am sure Ritz can find one just as good or better, and that would earn him $65,000 a year, forever or as long as that interest rate holds up. For me that has been the lowest rate I have been given in 17 years. It was recently as high as 2.25% and 3% a few yrs ago.
So, you see, while your idea is right (i.e. he has to make hay while the sun shines) your assumptions are a little too pessimistic.
This is the reason I laugh when I read about any Football or Basketball or Baseball star having financial problems after they retire or their career ends due to injury. You just have to make all kinds of mistakes if you made a good salary for 10 years to ever run out of money.