Wow, that’s more S6’s than I’ve seen in person, anywhere. Outside of JHM’s shop (I don’t count that, because their shop is an S6 magnet), I’ve only ever seen I think 4 S6’s. 3 of them were C7’s, and the fourth was a black C6 just like mine, the only other C6 I’ve ever seen in person (besides at JHM). Now that I think about it, I actually did spot a 5th one in Athens, Greece a couple years ago, which was also a black C6.
On the other hand, I see S4’s and S5’s almost daily. Not sure why the S6 ended up being so unpopular, it’s probably the coolest car Audi has ever made besides the R8. Maybe the price point was/is just not really in the right spot for north american sales.