I believe that the salary for non-national players is slightly higher, the rationale being that it takes more money to get a person to move away from their home. Maybe someone can confirm this.
Also, as mentioned above, there is more cash from merchandise for national players.
Basketball is an international game now. Just take a look the roster of any league in the world and I think you'll find, just like in BB, the higher the league, the more likely there will be players from other countries filling the rosters, particularly as the starters.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!