Why Did Prince Turn Down Nas?

During an interview Nas reveals that in the late 90's Prince turned him down for a proposed collab.

Nas says at his 'I Am..." album release party he told Prince, "Yo, look, man, let’s do this. Let’s do this song.’ And he was like, ‘Do you own your masters?’ But he blew my s–t because I was like, ‘I don’t. And I’m far from it, because I owe this label like four, five albums’ . . . I was like, ‘Damn.’ ”

Nas said after the party Prince taught him a valuable lesson in saying "When you own your masters, give me a ring.”