Do you not think he’d be happy at a lower ranked D1? Because it is a headcount sport, I think the most money might come from a D1. As others have said, a D3 or D2 merit is going to be about half tuition for a good, solid student. If he can get the other half tuition at a D2 for athletics, that is still going to leave all the r&b, books, travel, etc. D3 is even worse as you may get the 1/2 tuition in merit, but the other half would have come from the family.
Playing the sport might be the hook to get into a higher ranked school, but then you have to pay more.
What type of school does he want? Tons of D2 in the SE states, the PA state schools (West Chester, Bloomsburg, etc) and sprinkled across Ohio and Missouri. They might not be more appealing to him than lower D1 schools. Has he looked at schools like U of Denver, where they are D1 but not really known for basketball (hockey, lacrosse, skiing bring in the national championships)?