How often does a celeb popular enough to attract that kind of crowd actually have to fly commercial? I guess out of the main TPAC hubs on the West Coast...flights beyond the range of most private jets...??

When we get a significant celebrity in Kansas City, they land at the downtown airport (MKC). I've driven by there and seen fans gathered there along a fence, 50 yards or so from where the jets park, when someone especially "big" is flying in for a concert or whatever.