Yes, but at the same time if the D-League did have money then they could buy that star power. I could watch a team full of Dee Brown level players. But those college stars who don't translate to the NBA want to go overseas where they can make decent money. Sorry completely off topic.
I do not believe there is a market for it, that is why even bigger league efforts (e.g., ABA, USFL) eventually failed. Between college basketball and the NBA, there is not much space IMO for higher level NBDL. Europe is not the NBA, but there is local interest for basketball, especially in the absence of college (or even HS) basketball following.
Some external observes also exaggerate on the easiness to get big money in Europe. Low-tier teams do not offer much more money than D-league. Better, but not much. Top tier (i.e., Euroleague teams), there is indeed very good money, but college stars who do not make the NBA have little chance of making it right away. Euroleague teams are dominated by top international players and veterans, ex-NBA players who had spent more than a cup of coffee in the NBA, or college players who have proved themselves at mid-tier teams. Best scenario is to get a contract with a mid-level team in a good league (e.g., Brandon Paul this year with Joventut Badalona) but it took even Brandon Paul quite some time to reach there. With the emergence of international basketball, it is has become a lot harder to get the better contracts in Europe.