Follow the money. The flip side is that following the money may be good for your wallet but bad for your career development.....lots of players end up moving to bigger/richer clubs and losing playing time, when they might have been better off staying at a "poorer" club and getting more playing time.
But that doesn't need to be regarding players from other Continents, in Europe players from Leagues with less money when they have more talent they leave for richer leagues. Don't see where is the problem, ok a bit more of regulation would be helpfull to keep players more time on their local leagues to develop their game, but honestly you cannot forbid a player of wanting to earn more money, if it's in Europe, USA, China, Brazil, who cares?