It's absolutely not all Harleys, but it's hard to know how many, exactly, because you can't hear the stock ones (or your own thoughts) over the loud ones. I worked a flag station at the last Indy MotoGP, and one of the more amusing moments was when the undercard Harley race was happening and the race bikes went by but weren't as loud as the street bikes outside the venue.
I also lived in a small town in Montana with an annual Harley rally, and while many of the attendees were certainly in those doctor, lawyer, etc., demographics, the noise level was just absurd. They also spent a ton of cash at the restaurants and bars, so there was a significant benefit, but if you didn't work in the service industry, it was an excellent weekend to go camping.
All that said, I kinda want a Pan America. Not in the budget anytime soon, but I'm a bit soured on BMW given the limited dealer network in the U.S., especially out west.