Let me explain myself better by looking at the example of Batum. His club invested a lot of money into finding him, developing and training him, and giving him playing time to make a name for himself. They also invest in plenty of other young players who won't succeed. After all, no player is going to develop on a one man team. Their tangible gains are a year or two of good play from him for a fairly low salary before they lose him for nothing (his contract expired, so the Blazers didn't have to pay a buyout fee) to the NBA. France likewise invests in basketball infrastructure and the maintenance of the league, only to see what could be one of their most marketable players leave while he's still a teenager.
Where's their compensation?
note - you could also rightly argue that Batum's success in the NBA leads to intangible gains for the club as well as country, notably when recruiting new youth players, but that's impossible to quantify.
to directly respond to your post BBert, NBA teams know prior to signing a European player that he's very likely to want to play for his national team. They're well aware of the risks inherently involved with signing a Euro.