What you seem to be saying with your RL analogy is that any team in division III or lower should sell NT caliber players to teams in higher divisions. Right?
Yes, but to a point. At some point the very best players should end up in the highest divisions since that's what happens in real life. Otherwise what's the point of competition, or having a sports "simulation"?
It's up to the manager to hold onto a player or not, even if they choose to hold onto a very expensive player to the detriment of their own club. A manager's goal should be to win and promote, not have the best player(s) in the world.
Please don't infer this as meaning that I believe the best players should be given to the top teams or that top teams should be entrenched at the top. Movement between divisions shouldn't be reliant on having one amazingly skilled player over having a depth of good players.
"Well, no ones gonna top that." - http://tinyurl.com/noigttt