Huh? All of them grew up and lived in Compton and/or South Central. When did that become upper middle class? And do you have any reference for them being music industry insiders?
As far as upper middle class record industry insiders - Sure, Dr Dre net worth is projected to be $810 Million. He did Beats and Death Row Records etc.
http://www.celebritynetworth.com/richest-celebrities/richest...
Ice Cube at $140 million http://www.celebritynetworth.com/richest-celebrities/richest...
Easy E was estimated at around 8 million. http://www.therichest.com/celebnetworth/celeb/rappers/eazy-e...
etc.