That is the minimum contract amount. I'm not sure that anything has indicated that he signed for the minimum. The Mavericks had enough cap space available to offer DeAndre Jordan and then got turned down, so I'm sure they could have offered more than the minimum.
I think it's hard to compare European salaries. I believe they have risen greatly in recent years. Salaries usually are written in euros and listed as net amount after taxes, and oftentimes, the team pays the taxes for the player, so he's really getting much more. Many European players also get paid various living expenses (housing, utilities and even maids). When all of that is taken into account, some guys make the equivalent of more than $10 million American. But the number of guys who make millions are minimal. It's hard to say how much money Ndour could have received in Europe, but he probably could have gotten more. Most players are willing to take a little less to try to make it big in the NBA.