Someone over on the Tesla forums was aggregating S/7 series sales from public records and they was a significant and sustained drop since the S was introduced.
That's about the 3 series, which matches my experience better. A 3 series is a much cheaper car than the Model S (or 7 Series or S Class). I have no doubt that people who had 3 Series are now considering Teslas, and much credit to Tesla for creating a product that convinces these people to spend so much more money.
Except S-Class sales went up in 2013 and skyrocketed in 2014. Overall it seems like the introduction of a new model by Mercedes had far more effect than the Model S and then it fell off because it got older. 7-Series sales were probably also mostly affected by an ageing car.
https://www.reddit.com/r/teslamotors/comments/6dj815/tesla_m...