Generally the lower the cost the bigger the crowd. When I had a choice I shopped at the most expensive grocery story and avoided the discount gas stations, because that way I avoided the crowds and the long lines. Now it's twice as far to the next-nearest grocery store so any benefit from finding a more expensive store is lost, and my "gas station" is the electric outlet in my garage, where there's never a line. And the electricity at my house is free.
Realistically, as luxurious as my Tesla is to me, my sister, who drives a Lexus or a Mercedes (not sure just at present, she's had both at different times) would consider my Tesla primitive. Her car has cushier seats, more leg room, smoother suspension, is easier for a grossly obese person to get in and out of, and if you don't close a door all the way it finishes closing itself for you. It has a bunch of features that are worthless to me but that she demands. To her, buying gas is an unavoidable inconvenience because a Tesla would be unthinkable to her.
That's probably why many of those people at the Costco gas station are not buying Teslas.
But plenty of them are. I mean it's statistically unavoidable: Tesla is selling so many cars that some of the buyers must have gotten their last tank of gas at Costco.