Wejo in raising up the 800 guy who runs 2:06 brings up the main point.
If they get even reasonably good at running, even just winning a few races with a prize of $100/$200 that is very reasonable money for them! On the other side for someone in the US/UK then to be totally honest it's a nice bit of pocket money but really doesn't last for very long. Simple fact is that if distance running were as well paid as investment banking (well... pre-crash...) we'd see plenty of people putting in 100 hours plus weeks etc just like they do in industry. Running is some of these Kenyan's investment banking.
Noticeable that your guys perform an awful lot better up to and in college than our guys in the UK do - that's partly the set-up and partly the knowledge that scholarships are out there and available which means athletes get something material back for their training which isn't present over here.