What causing a rubbing noise when I turn?

What is your question?

Any ideas of what could be causing a rubbing sound when I turn? No, it's not the tires rubbing on the wheel well although that's pretty much what it sounds like. I've been told "It's your front ball joints" and "It's your bearings". Had both of those fixed - no improvement. Now I'm being told it's my rear differential. I'm not sure I'm buying that one because I had a friend stand outside the vehicle while I drove slowly around in circles in a parking lot. He said he could see the front passenger tire vibrate when I was turning but not the driver's side. The vehicle only makes the noise when I'm turning and moving (doesn't matter if I'm going forward or in reverse or right or left, but it doesn't make the noise if I'm stationary), and I can feel the vibration not only through the steering wheel, but also the floorboard and gas pedal. Power steering fluid is OK. Brand new tires with no odd wear patterns. I'm tired of the auto shop saying what it MIGHT be and then charging me to fix something that wasn't the problem. I can shoot in the dark by myself without getting a $1000 bill. Any suggestions?