Of course you're right about this--middle-class and poor people can't afford to play in the big leagues. (And $50K would not be enough even to lease a horse at that level, much less buy one. International-quality jump horses and show hunters are in the high six figures and low seven figures; top dressage horses can be in the ballpark of $10-20 million.)
My point is that your young friend and my daughter cannot compete with Springsteen, unfortunately. The top people compete with each other.
But among those who actually are competitive--those who have the fancy horses, the trainers, the physical plant, the six-figure trailers, the everything--the winners work hard and are talented.
Alas, show jumping on the international circuit is not like basketball. You can work incredibly hard and go up the levels through sheer determination to a certain point, and then you absolutely stop. I have friends who are teachers and hairdressers who are showing on the FL circuit, but only people surnamed Ward, Onassis, Bloomberg, Springsteen, Firestone, etc. go on and compete with each other at Aachen.