IMHO it's his connections to people (World Wide Wes / NBA General Managers and personnel people), along with the fact that he makes it known he's trying to get kids to the NBA first and foremost. The whole college thing is secondary, and many of one-and-dones could really care less about having to do college; it's that obligatory step they have to take to get where they want to go.
And despite what Cal says about the "lifetime scholarship", I don't get the feeling most of his kids are serious about a degree or trying to pursue one. After UK's response during the Bledsoe controversy, I have doubts as to how demanding the 1-year curriculum is in Lexington.
You should probably add, "He gets high class hookers, unlike the skanks that Louisville gets......and the untraceable debit cards don't hurt either."